Since your rich friend believes in you and is not 100% dedicated to this business, you can shape the contract in the way that you and your friend (who is not investor) can make strategic decisions about everything alone.

Decisions about financing & selling company etc you make all together.

I am working for over 1year on my startup, if someone at the beginning gave me $30k, I would give him 25% of equity without asking anything or even more.

Even right now I would rather accept $30k investment in return for 25% rather than get funded by VC funds which offered me $100k for 10%, because their contracts are shit! And actaully they want to control everything..

So, do not worry about, VC funds & investors are more likely to control you than your friend.

I will tell you model how to calculate % of equity that your friend deserves?

Well your idea at this stage is worth 0

How many hours did you invest into this project? And according to your previous job (or something), how much 1working hour by you is worth?

You can make estimation : okay I worked for 1year, 5hours daily, 1h = 20$

365days x 5h = 1825h × 20$ = 36.500$

This is how you can be fair to him