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.
It's a reality of life as a freelancer that many of the jobs I take on are uninspiring. This is an attempt at finding some of the type of jobs that I would really enjoy working on, and hopefully encourage someone to take the leap on a project that may have otherwise stayed on the shelf forever.
For me, I'm hoping to find people and projects that I'll get excited about working with. Giving away $2000 of work for free is about as much as I can possibly justify. I've brought a number of projects through from start to finish (complete code base, from scratch) in under 40 hours, and in this case it would represent the difference between a project costing $1200 and the same project costing $3200.
This could also be enough to get a functional prototype in place to impress investors, etc.
I also find it hard to justify working on my own projects when there's client work to be done.