Is it a bad idea to use a HELOC to pay the down payment for my first short term rental investment?

You can collect a down payment in many cases.2.

Also, the enemy method as made popular by Luke Carl is ultimately the best tool in your pocket! 

Me and my fiancé are wanting to try and purchase new construction homes in class A to B neighborhoods (275-350K) and put 20-25% downs and live in them for 1-2 years while we save another down payment and then eventually move on and make it a rental.We are not looking to scale rapidly.

Rents go up, refinances bring payments down, etc. 

The greatest obstacle in the way of the desire to expand portfolios is the need for cash to use as down payments. 

If I were able to acquire my next investment through cash and/or bridge loan, install my section 8 tenant and show a couple of months of rental payments, is there a lender out there that would use that lease and its accompanying Housing Assistance Payment contract I would have with the local housing authority? 

However, his mom's offer to co-sign shows commitment to ensuring rent payments.

Maybe they can make payments.

Spreadsheet Buying Subto (Subject To) with the (BOMSTSLO) ™ Method - Just a suggestion for those who want to jump ahead in investing - this is an actual deal recently done in AZSo, what's the difference between using ...