Or my property management website (rentecdirect.com) allows for online payments by card or ACH. 

LOC credit can be true cash which can have advantages and you don't need to have a lender approve your deal or go through draw process.

So I start looking at properties in my town, and I start to pull cards of houses that are going pretty cheap. 

Read Charles Becker of Duke University's article on this very topic for greater insight.Another difference is that Class B/C apartments typically need a huge amount of expensive cap-x to maintain their occupancy, while mobile home parks need a much lower amount since the park does not own the homes (or at least many of the homes in most cases), although this is true whether there is a recession or not.The final main difference is that apartments sell at much lower cap rates, so there is less cushion in the event of a recession, while mobile home parks still sell about 1 to 2 points higher in cap rate, so you have more flexibility to contend with the impact of a recession, whatever it may be.

In less than two months I had a fully renovated and rented property, was in a position to refinance, and had gained valuable experience for the future (knowing how much things cost, knowing how much time it takes to complete a rehab task).In regards to management, it is definitely true that managing 2-3 tenants is more work than just 1, so it's really dependent on how much time you have and how you value your time.

The same is true for all the burbs in the area.

Is it true you have to finish paying it off before taking another one out?

I'm the son of a retired CPA but not one myself, so my understanding of tax codes is only at a moderate theoretical level of why they are the way they are and how they work on a big scale, not the finite details to give true tax advice. 

Is this too good to be true?

@Michael Noto that’s true.