Is the loan principal ever delivered in pieces over time? Not sure if this is the right place for this question but it's more of a theoretical finance question than a personal finance question.

So a loan has a principal amount that is given to the borrower in a lump sum, and the borrow then pays back that amount plus some interest. For example, let's say that George loans \$100 to Fred at 10% interest over 10 months. Fred then pays back at \$11 a month and is debt free at the end 10 months.

Is it ever the case that George lends the money in increments instead of a single lump sum? That is, George pays Fred \$20 a month for five months, while at the same time Fred pays back at \$11 a month for 10 months. 

I ask because this would be less useful to Fred but less risky to George.
Handing out the principal amount of debt gradually, in increments, is standard practice in investment loans extended by a bank to a corporation.  

The rationale is clear : the corporation wants to make an investment, say a new factory. The whole plan is laid out and the cash flows of the pre-operational, construction period are also detailed, based on forecasts or specific agreements with the suppliers (contractors etc) that will be involved. The bank checks and accepts all these, but it also wants to see the corporation deliver (both the corporation's part in the financing but also as regards the actual build up of the investment).  

So specific milestones are agreed between the two parties, and to each milestone a round of financing is agreed (these milestones become contracutal obligations, legally binding). Milestones usually include specific technical phases of the build up to be accomplished (say, the building's foundations are complete, or the power infrastructure has been installed, etc). 

In this way risk is reduced without hurting the necessary cash flow for the project. It also reduces the interest burden for the firm.