I own the two homes next door and rent them for 1425 and 1350/month plus utilities.  3% annual appreciation.I would be putting 20-25% down on these and would be cash out refi-ing from some other properties for the down payment or possibly paying cash for deal #3+4. 

Additionally, FHA loans also have MI paid monthly in the mortgage payment, which is usually either 0.5% or 0.55% of the loan amount (annual basis).

The goal is to pull cash out as soone as possible to recoup your down payment and enough for the next DP purchase. 

Consider all the things that could go wrong and see if the lease addresses them: unauthorized pets or tenants, early termination, security deposit, lease violations, late rent, eviction, lawn maintenance, parking, etc.5.

The maximum fixed-rate period seems to be seven years, and there is generally a balloon payment at 10 or 15 years.

Key point is WITH a SECURED border to stop the flood of 100k-300k monthly illegls. 

The problem is that your debt payments are going to basically wipe out that $400K profit unless there is room to increase revenue or reduce expenses.

How will the partnership cash flow cover the HELOC payments if interest rates increase?

you may have to save up until you have enough money to do so - down payment, closing costs, reserves, etc.House Hacking: What Is It, How to Start, and Strategies for Successit's a more powerful way to get started. 

When parents employ their minor child, the child is exempt from Social Security and Medicare (aka FICA) - if under 18.