Based on your financial expertise, provide your response or viewpoint on the given financial question or topic. The response format is open.

If one owns 75% of company shares, does that mean that he would have to take upon himself 75% of the company's expenses?
I think you're looking at the picture in an odd way. When each of you made your initial investments and determined what portions you owned, that gave the company capital that they could use to finance its operations. In return, you are entitled to the future profits of the company (in proportion to your ownership). Any future investment by either of you is at your own discretion. Your company now faces a situation where it would like to pursue a potentially lucrative opportunity, but needs more capital than it has to do so. So, you need to raise more capital. That capital can come from one or both of you (or from an outsider). Since that investment would be discretionary, what the investor gets is a negotiation: the company negotiates with the investor how much equity (in the form of new shares) to award in exchange for the new investment (or whatever other compensation you decide on, if not equity).