@J Newman to answer your HELOC question: yes, you can use those funds for business purposes if Dad is comfortable with that option. However, he (you) should keep it "clean" and not also use it for personal reasons. I have a HELOC in place on our personal residence and have used it exclusively for flips and spec builds. You are correct - the terms can be great and with the exception of the monthly interest payments, you control the payback schedule.
You can add a business or personal line of credit (LOC) as well if you can get one. For quickie emergencies there are always the "18 months no interest" options at Lowes or Home Depot along with similar terms from your credit cards (those checks you can write for a 3% fee and then have 12-18 mos to repay).
You mentioned great cashflow. And you mentioned Cap Ex. So it sounds like you are setting aside some funds. Perhaps you need to redirect some of that cashflow for a year or two to get things straightened out and maintenance caught up.
With 62 units you need to set up a reserve asset plan similar to what an HOA would do. Make a list of all assets and their components (how many roofs, refrigerators, heating systems, etc?) Note their ages and realistic life expectancy. Then figure out (in today's dollars) what it will cost to replace. Let's say you have an HVAC system that will cost $10,000 to replace and it should last another 10 years. Then you know that you need to be setting aside $1000 a year so you'll have those funds. These dollars can be parked in a savings account with longer term amounts layered in higher paying CDs so that you are somewhat keeping up with inflation. You could also add 2-3% to the amount set aside each year to account for the increased cost too.
It is going to take a disciplined plan to deal with the short term "musts" and then set yourself up for an easier time in the long run. Good luck!