After we signed for the mortgage, he decided not to move in even though the conditions of the mortgage required him to do so.

It's also not rented yet so there is no income to DSCR, the tenant would need to be in place or at least moving in prior to closing.That doesn't mean you couldn't get a negative DSCR loan or bridge option, there are many options.

Say if I have $5,000 to work with, is it possible I can get an Airbnb and if so how ?

Let's say you want to stay conservative and only take 50% LTV, or $500,000.00, so that you don't have to sell anything in case of a market correction and there's a margin call.Step 2:  Purchase a rental property, all-cash, with that $500,000. 

So let's say we buy a SFH or a duplex for $125,000 putting 20% down.

So, on a 540K loan,  the VA funding fee on IRRRL is .5% or 2700, escrow would likely be 3000-4000, whatever county taxes, maybe the finance company charges underwriting and processing maybe 1000-2000, and other fees you might have to pay ~1K.

So if your flooring is So if your flooring is light Oak, and the rest of your kitchen is white your backsplash can implement some light, beige and gold colors. 

I'm looking mostly for if I buy a 4-unit quadplex (example, or Triplex), how to calculate NOI, Monthly Cash Flow, Rehab, Cap Rate, Cash-on-Cash, etc.For example, whenever I find a property on Crexi, Loopnet, MLS, etc. the NOI sounds good but when you factor in mortgage to get the cash flow, it's almost always negative.I also don't know how to properly calculate a rehab to see ARV so that may be the other issue.

So there is that..

Thanks so much!