An important lesson in business for te future is that the idea comes first. Never spend money on a business if here’s no concept/idea behind it. Once you have the idea and have started implementing it then worry about the domain/site/branding etc.
In essesne your post is looking for a ‘partner’ who’ll share their idea with you, have to implement most of it themselves all in exchange for a domain name that has limited potential.
If you’re a developer then it’s a bit of a different story but nonetheless should know that you don’t buy domains for a project you don’t have.
Domain buying is impulsive (I was guilty of it at one stage too) but lost enough to realise that unless you have something concrete, 9/10 times it doesn’t pay off.
excatly what i was going to say to him