This LLC will give/loan(not sure what the correct word is) money to my cousin's Company, and there will be an agreement to get a percentage of equity in the construction project(i.e each of the 6 investors may get an apartment after the construction project completes).

Somebody thought it would be a good idea to do a major interstate toll road project and build a new stadium at the same time. 

Are there any creative but legal ways to use my personal funds and the SDIRA on the same projects?

It will be a project that involves some $$ investments.

They will typically ask for 15-20 % of the total project costs and at least 6 months of mortgage payments to fund your project.

Good Condition, under served market, and buying at $19 per square foot.....Projected to be worth double acquisition cost within 12-18 months....The point being that Cap rates are a good place to start but a terrible place to stop your analysis:)  Good luck in what I know to be a phenomenal niche!!!!

I don't want to carry a note forever (love the idea of the income, but I need the cash for other projects), but I'm willing to do it for a year or two.This seems like a puzzle to me - all the pieces are on the table, I just can't see how to fit them all together to complete the task.

In my spreadsheet I'd have more exact math, I'm just simplifying for discussion sake.So, you account for these fees when doing your projections? 

That's my project for the summer. 

we can place new tenants that we vet and move rents to market price.Disadvantage, Longer project time.