why would closing price of a stock be different from different sources, and which would you take as the real price?
"There is more than one exchange where stock can be traded.   For example, there is the New York Stock Exchange and the London Stock Exchange.  In fact, if you look at all the exchanges, there is essentially continuous trading 24/7 for many financial instruments (eg US government bonds). The closing price quoted in papers is usually the price at the close on the NYSE.  However, options close after that and so there is after-the-close trading in many stocks with active options, so the price at the close of options trading at CBOE is often used. The ""real"" price is always changing.  But for the purpose of discussion, using the closing price in NYSE (for NYSE listed stocks) is pretty standard and unlikely to be questioned.  Likewise, using Bloomberg's price makes sense. Using some after-hours or small market quote could lead to differences with commonly accepted numbers - until tomorrow :)"
I work on a buy-side firm, so I know how these small data issues can drive us crazy. Hope my answer below can help you:  Reason for price difference: 1. Vendor and data source Basically, data providers such as Google and Yahoo redistribute EOD data by aggregating data from their vendors. Although the raw data is taken from the same exchanges, different vendors tend to collect them through different trading platforms. For example, Yahoo, is getting stock data from Hemscott (which was acquired by Morningstar), which is not the most accurate source of EOD stocks. Google gets data from Deutsche Börse.  To make the process more complicated, each vendor can choose to get EOD data from another EOD data provider or the exchange itself, or they can produce their own open, high, low, close and volume from the actual trade tick-data, and these data may come from any exchanges.  2. Price Adjustment  For equities data, the re-distributor usually adjusts the raw data by applying certain customized procedures. This includes adjustment for corporate actions, such as dividends and splits. For futures data, rolling is required, and back-ward and for-warding rolling can be chosen. Different adjustment methods can lead to different price display.  3. Extended trading hours  Along with the growth of electronic trading, many market tends to trade during extended hours, such as pre-open and post-close trading periods. Futures and FX markets even trade around the clock. This leads to another freedom in price reporting: whether to include the price movement during the extended trading hours.   Conclusion To cross-verify the true price, we should always check the price from the Exchange where the asset is actually traded. Given the convenience of getting EOD data nowadays, this task should be easy to achieve.  In fact, for professional traders and investors alike, they will never reply price on free providers such as Yahoo and Google, they will most likely choose Bloomberg, Reuters, etc. However, for personal use, Yahoo and Google should both be good choices, and the difference is small enough to ignore. Typically the settlement price for a financial instrument (such as AAPL stock) underlying a derivative contract is determined from the average price of trading in that instrument during some short time window specified by the exchange offering the derivative.  (Read the fine print on your contract to learn the exact date and time of that settlement period.) Because it's in an exchange's best interest to appear as fair as possible, the exchange will in general pick a high-volume period of time -- such as the close of trading on the expiry date -- in which to determine the settlement price. Now, the expiry date/time may be different from the last time at which the option can be traded, which may be different from the underlying settlement time.  For example, most US equity options currently expire on the Saturday following the third Friday of the month, whereas they can last be traded at end-of-day on the third Friday of the month, and the settlement period may be at a slightly different time on the third Friday of the month.  (Again, read the contract to know for sure.)  Moreover, your broker may demand to know whether you plan to exercise the option at an even earlier date/time. So, to answer your question: After-hours trading can only affect the settlement price of an underlying instrument if the exchange in question decides that the settlement period should happen during after-hours trading.  But since no exchange that wants to stay in business would possibly do that, the answer is no. Contract expiry time, contract exercise time, final contract trading time, and underlying settlement time may all fall at different dates/times.  The important one for your question is settlement time. Insurance - get estimate from an insurance agent who works with policies for commercial real estate.  See comments below regarding incorporation. Taxes - if this was basic income for a simple LLC, estimating 25-40% and adjusting over time might work.  Rental property is a whole different prospect.  Financial experts who specialize in rental properties would be a good source of advice, and worth the cost.  See below regarding incorporating. Real estate appreciation - not something you can count on for developed property.  Appreciation used to be almost guaranteed to at least keep up with inflation.  Now property values are not even guaranteed to go up.  Never have been but the general rule was improved real estate in good repair appreciated in price.  Even if property values increase over time, rental properties depreciate.  In fact, for rental properties, you can claim a certain rate of depreciation over time as an expense on taxes.  This depreciation could mean selling for less than you paid for the property after a number of years, and owing capital gains taxes, since you would owe the difference between the depreciated value and the sale price. Related to taxes are local codes.  Some areas require you to have a property management license to handle buildings with more than a certain number of units. If you are going to own rental properties, you should protect your private financial life by incorporating.  Form a company.  The company will own the property and hire any maintenance people or property managers or security staff or any similar employment activities.  The company takes out the insurance and pays taxes.  The company can pay you a salary.  So, bottom line, you can have the company pay all the expenses and take all the risks.  Then, assuming there's any money left after expenses, the company can pay you a manager's salary.  That way if the worst happens and a tenant breaks their hip in the shower and sues you for ONE MILLION DOLLARS and wins, the company folds and you walk away.  You might even consider two companies.  One to own the property and lease it to a property management company.  The property management company can then go bankrupt in case of some sort of liability issue, in which case you still keep the property, form a new management company, repaint and rename the property and move on. TL;DR:  Get insurance advice from insurance agent before you buy.  Same for taxes from an accountant.  Get trained as a property manager if your local codes require it (might be a good idea anyway).  Incorporate and have the company take all the risks. The price of a share has two components: Bid: The highest price that someone who wants to buy shares is willing to pay for them. Ask: The lowest price that someone who has a share is willing to sell it for. The ask is always higher than the bid, since if they were equal the buyer and seller would have a deal, make a transaction, and that repeats until they are not equal. For stock with high volume, there is usually a very small difference between the bid and ask, but a stock with lower volume could have a major difference. When you say that the share price is $100, that could mean different things. You could be talking about the price that the shares sold for in the most recent transaction (and that might not even be between the current bid and ask), or you could be talking about any of the bid, the ask, or some value in between them. If you have shares that you are interested in selling, then the bid is what you could immediately sell a share for. If you sell a share for $100, that means someone was willing to pay you $100 for it. If after buying it, they still want to buy more for $100 each, or someone else does, then the bid is still $100, and you haven't changed the price. If no one else is willing to pay more than $90 for a share, then the price would drop to $90 next time a transaction takes place and thats what you would be able to immediately sell the next share for. Stock valuation is a really sticky business, although they are ways to value it, it is somewhat subjective(expectations are calculated). But it will be at premium most likely, can't tell how much without any numbers.(wouldn't be able to tell with the numbers as well since i do not have any knowledge in the sector) Here are some significant factors affect the company stock price performance: Usually, profitability is known to the public through the financial statements; it won't be 100% accurate and people would also trade the stock with the price not matching to the true value of the firm. Still there are dozens of other various reasons exist. People are just not behaving as rational as what the textbook describes when they are trading and investing. It just states that the price doesn't justify the valuation which is not a factual statement. Also this is based on someones opinion of the companies P/E. The P/E was published and public information and idiots on both the buy and sell side jumped in.   The article does not make a factual claim about Fraud (cooking the books), Francine McKenna speculates that management  and auditors cooked the books. "Some technical indicators (e.g. Williams %R) indicate whether the market is overbought or oversold.   ... Every time a stock or commodity is bought, it is also sold. And vice versa. So how can anything ever be over-bought or over-sold? But I'm sure I'm missing something. What is it? You're thinking of this as a normal purchase, but that's not really how equity markets operate. First, just because there are shares of stock purchased, it doesn't mean that there was real investor buyer and seller demand for that instrument (at that point in time).  Markets have dedicated middlemen called Market Makers, who are responsible to make sure that there is always someone to buy or sell; this ensures that all instruments have sufficient liquidity.  Market Makers may decide to lower their bid on a stock based on a high number of sellers, or raise their ask for a high number of buyers. During an investor rush to buy or sell an instrument (perhaps in response to a news release), it's possible for Market Makers to accumulate a large number of shares, without end-investors being involved on both sides of the transaction.  This is one example of how instruments can be over-bought or over-sold. Since Williams %R creates over-bought and over-sold signals based on historical averages of open / close prices, perhaps it's better to think of these terms as ""over-valued"" and ""under-valued"".  Of course, there could be good reason for instruments to open or close outside their expected ranges, so Williams %R is just a tool to give you clues... not a real evaluation of the instrument's true value."