you could set it up so your old llc owns 75 percent of the new llc. that way he doesn't own any of your other projects.

But, before your go through all the work, what is he going to do for his 25%? how are all the monthly expense getting paid. hosting? email? etc.

let's say you and your partner put in 1000 hours at $35/hr that's 35k worth of development is he putting $12.5k worth of value in?