<p>I doubt that it would cost more than $150 or so, possibly less.
The reason that I suggest it is that even though you are related, it could help to talk through the implications and to make sure that the contract is written so that both of you are very clear about what's expected.</p>
<p>For instance, if it were to say, "payment will begin 6 months after son finishes school," that may be too vague. For instance, what if you had to take time off because of illness. It wouldn't be fair to expect you to pay back the $ if you were ill, but if there were then some dispute between you and your mom, she might expect you to do that.</p>
<p>If you dropped out of school because of some really stupid reason, and the contract used the vague language I gave as an example, theoretically, you could refuse to pay because you could say you hadn't gotten your degree.</p>
<p>(Given your high level of motivation, I honestly am not anticipating that you'd drop out for a dumb reason nor am I thinking you'd skip out of your promise to repay the loan. I do think, though, it's helpful to have a real contract and for both of you to think of the implications. It also would be a good way for both of you to find out about contracts and loans).</p>