I also recommend separate checking and linked savings account with debit card. Start the account with the minimum to avoid monthly fees. I give this account number to the property manager to use for his rental and security deposits. I use the debit card to make purchases for the property. Security deposits can be moved to the savings account. I sweep the excess rental funds into another account so I never have a high balance in the account in case of some type of fraud.
I have a home warranty on every property except for one that has limited "systems"*. I include the costs of the home warranties in my economics. These warranties have saved me many times when expensive systems break down - which always seem to come at the worst times. It is true that they do not cover every breakdown and you have to pay for certain items but I have mastered these contracts so my managers know when to call the warranty company and when to dispatch their own service personnel. I have multiple contracts so I even get a 5% discount for multiple properties.
My warning to you is - if the AC/Heat failed tomorrow do you have enough cash reserves to replace the entire system with upgrades for code? If not let the warranty do it. You will have to pay for ducting, disposal and a few other things. My latest one failed in May and cost me $1200 while saving me $8000.
What else has the warranty paid for a new garage door, a new wine refrigerator (most will pay for 3 refrigerators in a house), a new induction cooktop ($1500), two microwaves and several dishwashers. To date, warranties have replaced five AC systems with upgraded units. FYI - this is why I also buy used appliances as I have no fear of them failing. How much does that save me? Thousands of dollars.
* Limited Systems - basically if the property does not have forced air AC/Heat then I will usually not choose a home warranty but I may buy specific extended warranties on any newer appliances.