I think of my time as a finite resource that requires allocation. I have big buckets into which I divide these roughly like the following.

Professional Work

> Short-term revenue (freelance/consulting) hourly/day rate

> Long-term deferred at-risk revenue (my own product-like projects and equity based compensation arrangements)

> Charity (this could include favors to friends, work donated or deeply discounted to a non profit org that you support and open source contributions) in this category you are working for intangibles like the common good, reputation and the satisfaction of having contributed to something bigger than your own direct interests.

Personal Life

> Interpersonal relationships (family, friends, neighbors etc.)

> Faith community or causes that you support (direct participation - may have little or nothing to do with your professional skills)

> Personal development - exercise, learning etc.

> Leisure/Entertainment

When friends approach you with their great idea - you can explain you only have so much time and it is not prudent to put too much of it in the deferred at-risk revenue bucket. If they are willing to move it to the short-term revenue bucket you can consider them as a client but your at-risk bucket is already full. If you feel like they are a good enough friend that you might just do it as a favor then do it as an investment in your friendship but limit your time to something comparable to helping your friend build a new deck on his house ...the kind of time investment that is appropriate among friends. However, if you do this as a favor be clear about what you are doing, where the limit is and that you are not committing to long-term support.

Hope this is helpful in some way.

I suggest watching this talk: https://creativemornings.com/talks/mike-monteiro--2/1

The speaker is eccentric and sometimes unhinged but many freelancers need to hear it.

Just do it. If they are not willing to pay, they are not committed to the project enough.