The seller has been unusually involved with things even after selling the property to me - they let me know today that there was no hot water and they had to replace the heater, and are charging me ~$700.

I added HVAC to the two end units and fixed the water heater in the other.

My only real expense has been electric and water each month at less than $30 and a years’ worth of taxes that will be $3600 and which I’d factored into the total cost.

There are great resources on BP and individuals here that remember sticking their toe in the water for the first time. 

Oh, BTW you mentioned a past water leak under that cabinet. 

My parents' NEIGHBORHOOD is 2, because the grad students were trashing the yards because they didn't water or mow regularly, and the neighborhood also needed to throw out a frat that was misbehaving.

My thought is to put together a database of big ticket items (roof, siding, water heater, appliances, etc) that I will update with prices every year or so. 

Check the water and sewer accounts though- those are leinable in most parts of PA. 

I have a condo that is about 15 years old and along with that are the water heater and A/C unit.

Maybe a leaking sink or someone that didn't understand a kitchen faucet enough to get hot water out of it.Had someone lose a kayak, but I knew what part of the lake to go find it.