Or rent out, refinance , and recoup money else where knowing what I know now .

To finance the deal, I'm thinking of using hard money and heloc from 1 of my properties.

What @JDmartin said.......You'll lose money unless you hire a good GC.

So I throw them a bone and take money off rent for them to work on them over time.

There is still money to be had and a lot of opportunity but just make sure your location is good.

I was intrigued by the fact that you don't need a lot of money upfront to get in.

I think you may want to start of the arrangement in a more simple fashion.Ask for a loan in which he will get a stated return 6% to 12%.If you are both successful happy with this arrangement, upgrade to a partnership.I think a partnership off the bat makes things complicated.You will also likely make more money in a loan agreement if the project does well.

We currently have some money that we could use for renovations, but we don't know if we should use the equity for that instead or use it to put it on a different property.

You can even get better with CDs and money market with no risk.  

We have a relationship with a much larger developer who does multifamily, mostly apartments, and even they can't figure out where to put their money right now, because the math just aint mathing for them to build or renovate at the moment.