Hometown Heros is a second that is due when you sell.
It's a mortgage loan program that might help keep your
low interest rate first while accessing equity to purchase
another property or add additional housing space.
Problem is you cannot refinance when or if rates go down as you
owe 101% of the value. Values are not rising.
If you found a single family or duplex and added a ADU
you need cash to pay for the ADU and installation.
3-4 units you need a much larger down payment and does not work.
If you could find a single family with existing ADU that works with your plan.
Live in the ADU and find a tenant for the house.
Short term rental is more difficult as FHA or conventional lender appraisal
does not give you value for the furniture or not real estate assets
that a STR for sale has as part of the price.
STR can get banned in a city in the future.
FHA uses the value of long term rental income knowing
that you may be forced to that as the only choice.
We cannot know what the future brings. If your business
model is to invest in AirBnB or STR style management
you must closely monitor the tenants you rent to.
Being the neighborhood frat party house or Rave house
is going to get your neighbors up in arms and limit the future.
Clean up your trash, manage professionally, vet your tenants.
The above Case Shiller housing price index does not show
huge appreciation in residential real estate since the last crash
in 2008. Do not rely upon valuation increasing to carry you.