Are you new? Buying an "Off Market" property with "Subject To" and "Wraps" & Selling "Lease / Option"
When buying a property to cash flow, you need to know what your expenses are. The following is one I actually ...

No, this arrangement does not qualify as interest. 1099-INT would be wrong.This is a profit sharing arrangement, and the correct form is 1099-MISC.

My investors, which are just family members and are not in the LLC, they give me cash and in exchange I pay them a percentage of the profit after a house I previously acquired with said cash sells (buy, fix, sell).

Welcome to BiggerPockets @Hailey BarnesFlipping is a great way to make a profit in real estate.

Let’s look at Indianapolis IN; (not my market, just using it since it is a popular place)  https://www.redfin.com/city/9170/IN/Indianapolis/housing-market for a median price of $250K That's the range you want to start out in, as a beginner.Then we assume 35% of ARV (After Repair Value) to do the rehab, holding costs, sales costs and profit.

Cashflow is just 1/5th of the profit puzzle.

He's getting paid 30% of the profit rather than a GC fee...that's the headline.Whether you pay him a GC fee or you split the profit is not that relevant (assuming they are a similar amount). 

I have/ sold 4 properties in the lelast 4 months for a profit of 270k.

I estimate total construction costs will be around $1.3M–$1.4M.His initial idea is for me to cover the construction costs, and then we split the profit once the project is sold.How would you recommend structuring this deal?

I know it will take over a year's profit to do this, but the return over the next 20 years will pay off.