Just like the OP says in an above comment: working on 25 hours for free on someone else's project is more likely to lead to future paid work than working for 2

Just like the OP says in an above comment: working on 25 hours for free on someone else's project is more likely to lead to future paid work than working for 25 hours on my own projects. 25 hours is almost certainly not enough to get an MVP done, so whoever he works for will likely need to 'pay their way' through the remainder of the project if they want to get it finished.