Consider all the things that could go wrong and see if the lease addresses them: unauthorized pets or tenants, early termination, security deposit, lease violations, late rent, eviction, lawn maintenance, parking, etc.5.

When we reached our limit there we actually did a consolidation loan with a commercial DSCR loan where we paid off 5 Fannie Mae loans with a portfolio lender which opened up 5 more Fannie Mae slots for us.  

However, when someone breaks a lease early, they are often not in a financial position to pay those, so you can apply their deposit to those costs, and after that, good luck.  

Are you depositing your pay in the bank?   

I built into my analysis of each property monthly deposits into that account to cover those contingencies.  

If I think about canceling the contract, I am very sure I'll not get the 10% earnest deposit I already paid.

It has to be secured before we can close, the reason we have requested a 50% deposit and other balance paid once closed.

(Q3)Security deposit is another area that I need clarifying on.

What happens to original security deposit from original 12mo lease?

You could ask for additional upfront deposits (double deposit, last months rent) if you're confident, but I wouldn't unless they were $100 or $200 off the 3 times rule.