What percentage of equity do you give away for a down payment

[Anthony Vander Meer]

Hey all, 

I'm up to 14 units using my own money. I recently have been presented with a few very promising small multi family deals direct from sellers. I have some cash but want to keep it for the future market softening. I'm debating on bringing on silent partners/JV's for the down payments. What is a fair equity stake for the silent investor and pay back time frame? Any thoughts would be appreciated.