The correct answer is you give them as little as possible to make it worth it for all parties involved. Sorry for the answer, but it really needs to be looked at on a project by project basis.
I've seen JV partners take as little as 20% and as much as 80% depending on the deal. Typical ranges are from 20-50% however.
Questions to ask yourself when considering taking on an equity partner are:
Is this the least expensive money I can acquire to complete this deal?
Would the deal make sense if I was the equity partner?
What is the break-even point of the deal?
Is there debt service on the borrowed money? (There shouldn't be in an equity sharing scenario...)
Do I have a viable exit strategy to cash the equity partner out?
Does the equity in the property justify an equity partner?
To be honest if all you need is $1,000,000 to get this deal done I can help with that. No debt service on the $1,000,000 and you can keep 100% of the equity in the project. PM or email me for more information
Thanks,