[gojomo]

(1) risks lawsuit unless there's an ironclad purchase/assignment-of-rights with prior guy

(2) only you and he can weigh that prior progress against his future value, and each of your next-best-options.

(3) still fishy and seems irrelevant; if he's receiving cash-up-front from business for living expenses, that either -- (a) won't be paid back in fail-scenario, or (b) will be paid back, when there's plenty of money and it doesn't matter, in succeed-scenario -- then it's mostly like salary, and there shouldn't be brownie points for calling it a 'loan'.