However, it was an FHA appraisal, which as I understand it goes into the system. 

I engaged a licensed HVAC contractor to do my central air systems- I’ve been burnt in the past, so my code going forward, is to buy materials myself, and pay the labor upon completions or milestones- The issue with HVAC is suppliers will only sell to licensed contractors, not homeowners.  

@Lev PaleiWith the right systems, a good handyman could self-manage and do the upkeep on maybe 20 properly hardened SFR before maintaining them seriously started cutting into his time.

How many circulator pumps are on the system?

@Raul Velazquez Jr Everyone is different - some with an accounting background or general knowledge about accounting can handle tax prep on their own with one, maybe two properties.Others like to put systems in place and hire out right away, to free up there time to spend on more valuable tasks and actions.If the latter describes you, I would say start speaking with real estate savvy CPAs ASAP.

We have the intentions of keeping this duplex long-term as it is the start of our real estate investments, but want to know whether it is a wise investment to upgrade to central heating and air in Ohio given that we will have to run two sepearte systems and all duct work in addition to upgrading the electric box.

So Market Value is what houses are worth in the neighborhood versus Comps being based off the most recent sold property similar to yours?

My thought is if you have little to no experience and no money ( even if you have good credit) then you tend to have very little value to offer and can't command  half.In those situations you take what you can get as the person with the money is taking a higher risk with a newer investor versus a known investor that is very seasoned and experienced.Once you start getting experience then you can start looking for better sources of capital or renegotiate split of the next deal with current investor once showing a positive track record of success.  

After you have the septic systems inspected and everything checks out you can assume each one pumped every 5 years (assuming 1:1 septic to home ratio).

When a big ticket appliance or mechanical system of the house breaks and you have no reserves because you have no profit you’ll be sick to your stomache .