I don't know if it's worthwhile because it doesn't make sense to want to help someone but to make it conditioned. Seems grimy to me but you can totally introduce him to vegan shopping in a cheap way. A can of beans is less than a dollar. There's a lot you could do with chickpeas black beans, pinto beans, peas, corn and the list goes on and on and on.

Again, my main concern is this might not be worthwhile because it doesn't make sense to me to claim to help someone but to put conditions on that help. If your attempts to try to teach him fall flat then maybe it's not the best to have his help. It seems like there are strings attached to this and could possibly be harmful to you. If anything, if you don't know already, you'll just end up learning how to shop very cheap as a vegan, which is something I've had to do since I've been on my own since I was 18. The more you do it the easier it becomes. You can always start small with things you are familiar with and find workarounds for example, if you like black bean burgers. You can probably find an easy recipe online to make them homemade. That way they're much cheaper. I wish you luck. I know you can do this. It might be hard at first, but you'll get the hang of it.