No occurrence is too small.

I've also used traditional loans through regional banks and a few SBA loans. 

A good tax accountant can save you thousands of dollars by leveraging entity selection and formation, tax deductions, cost segregations, bonus depreciation and tax planning.I recommend finding an accountant who specializes in business taxation, financial planning and tax planning.I would also recommend looking for a accountant willing to work with you throughout the year.

One thing I continue to think about is how valuable 2-4 unit properties are becoming, and will continue to be, since Fannie/Freddie took the income restrictions from the 5% down conventional loan option for house hackers. 

They simply do Fannie, Freddie, FHA, VA, and USDA loans.

I am an aspiring serial house hacker based in southern New Hampshire actively searching for my second small multifamily deal in the Nashua area, but I've hit a wall with inventory being so tight in my local market.

Some banks and lenders will calculate your Heloc payment based on the Max limit even if you only have a small portion used due to preventive risk. 

I know a lender that does 15% down on investment loans.

I can only imagine that they got a bunch of big time investors and business loans to grow this out.

I currently own and self-manage two STRs in Maine and should be closing on a small 'cabin campground' with 10 cabins nearby that will also be operated as STRs.