IRS says it's inventory, in a business activity, not a long term investment.....subject to ordinary income tax, including both sides of SS/Med (15.3%).

How do you determine if a rental, fix and flip or buy and hold property is worth the time and effort?

As for you and your parents arrangement, you may want to seek the advise of an attorney to determine your agreement between you and your parents regarding the money.The HELOC is relatively a simple process.

The real estate is effectively inventory in a sales business, just like refrigerators or stereos.Passive sources of income such as interest (i.e. hard money lending), rents from real property, dividends and royalties are not subject to UBIT.This concept is documented in IRS publication 598.The ROBS program is an entirely different structure as compared to a self directed IRA.  

Trying to determine the best way to contract these deals and wondering what you’re advice would be?

Truly one of the best turnkey real estate agents in Cleveland You are proving to the world that hard work and determination really pays off.YOU ROCK!!!

I am seeking to determine if useful, and to what extent.  

They go direct to manufactures in China or wherever they can find the cheapest.As an investor, where or who you buy your inventory from determines your profit.I once hired an Assitant, and she told me she was an investor.

First, determine your real estate goals. 

As @Donny Widjaja mentioned, the determination of employee status should not be governed by the purchaser of the materials.