Put yourself in the bank's shoes. What do you care about? First the income to loan ratio. The income should include the house hacking rent (banks usually require a 2yr history on that to count, but any positive number counts). Second, your credit history. Third, the deal itself. If you can eloquently demonstrate how good a deal it is, i.e., the deal pays back the mortgage itself, you stand a good chance to be funded. But it is pretty difficult. You need to provide specific numbers with good justifications. So it is not the number of mortgages that counts. It is your paying back power that matters. Of course, the later mortgages will see a higher rate, because as you near your limit, the bank takes more risks.
As for LLC, I think it makes sense. Set up a LLC for later investments, so that if anything goes sour, your primary residence won't be affected.
You do not provide much detailed information about yourself. But based on the information I get, you do not have much cash at hand. If that is the case, it boils down to finding motivated sellers so that 1) you can put your creative financing to work (if the seller is not motivated, your chance of using your creative financing is very limited) and 2) getting an appealing price.
