In the unit I had a tech look at on friday it was a circuit board that cost $160 to fix.

Yes, the fees and interest rates are high, but ideally you’re in and out of that loan in less than 3 months, so the interest rate isn’t a deal breaker.

A circuit breaker could constantly trip. 

I rent a duplex to two groups of two tenants, so you`d think among the 4 of them, somebody could be home for a new AC unit to be installed.When they first notified me of the problem, I asked them to check the breaker, make sure the thermostat was set correctly, check if the unit was coming on at all etc and to let me know their findings.I heard nothing for ten days and figured it was working, but sure enough, when I contacted them to make sure, it wasn`t.I made an appointment for a tech to come out the next day, but none of them were available and couldn`t agree on a day they`d be home until several days later.When the tech came out, he got the AC working, but barely and it wasn`t worth fixing.I told the tenants I`d have a new one put in ASAP and scheduled an estimate for the next day.None of them could be home the next day, but I felt bad for them and their pets, so I offered to be there for the estimate.  

MO Statute 535.020Whenever any rent has become due and payable, and payment has been demanded by the landlord or the landlord's agent from the lessee or person occupying the premises, and payment thereof has not been made, the landlord or agent may file a statement, verified by affidavit, with any associate circuit judge in the county in which the property is situated, setting forth the terms on which such property was rented, and the amount of rent actually due to such landlord; that the rent has been demanded from the tenant, lessee or person occupying the premises, and that payment has not been made, and substantially describing the property rented or leased.The easiest way to prove that payment has been demanded is to serve a P/Q notice.

@Jeremy Willis this sounds like the typical seminar funnel circuit designed to get you in at a low price and only give you enough info to get you to purchase the next level of whatever they tell you you need.

I do know there's internal wiring that could lead anywhere so is turning off the breaker to the kitchen (where alarm is located) an option?

No venting but you need a couple of double poled breakers so I upgraded the entire system to 200amp.

I have changed some light fixtures and the 240VAC water heater.I did install a double pole 240VAC breaker and run temp power out to a large camper.Haven't had the need to do do anything more.

The Ironman race there is on the circuit and one of the largest attended in the world.