I am a fan of utilizing equity in existing real estate owned to build the rental portfolio though at the beginning, rather than just relying on money saved alone.  

If you plan on buying these properties using a mortgage its also best to begin the pre approval process and work with an investor friendly lender to help guide and educate you what the best product might be for your projects to make sure you dont already max out your borrowing power after the first deal.

The mortgage would prob fall around 1600-2000 range.

Quote from @Dennis Knapp: I Have one double that I live in i bought as an investment just to help pay my mortgage.

Buy a new primary home and rent out your existing home.

What I typically see investors do to get rolling is use a Heloc or cashout refi on an existing property to get the startup capital they need.

The mortgage is what your tenant is paying for your property. 

But I do have an issue with asking some of these pre-existing cabin owners to have to retrofit their cabin with the system and expecting them to have it done in a year or something. 

The load calculation made for the existing foundation were not factored into the initial design.

FHA has a lot more paperwork, up-front PMI, plus you have monthly PMI for the duration of the mortgage.