I used conventional financing through banks.

Most conventional lenders will want a minimum of 6 months "seasoning" and up to 12 months. 

Use the BRRRR one evaluating the 4-Plex using a conventional Residential Refinance loan.  

Make sure to clearly outline good and bad outcomes - who pays for what if the project ends up losing money, how much he’s charging for his labor and his workers labor?

If they are participating in the profits and not charging interest, they will be more like a limited partner than a lender. 

But since you mentioned your income I would assume you have a lot of responsibility at your day job.My advice is go conventional, a year and half ago they required a 10% down payment, im not sure what it is now. 

When qualifying for a loan, I’ve heard to go to different mortgage brokers/lenders to compare interest rates.

My question is, if I were to buy a property for 70k with an fha loan ( 2.45k down) spend about 10k in repairs, increase its value to 100,000 would I be able to refinance out of the fha loan to a conventional loan without having to live in it for a year?

Or find someone with a HELOC at 5%... they can draw on the HELOC @ 5%, charge you 12% and 3 points, and make that  spread as profit. 

We have conventional loan and honestly this is the first time I have seen anything like this before.