Obvious sagging of roof elements or awnings could mean damaged joists or rotting sheathing.

If you are asking about how to find a good neighborhood for you to live in, you can look at crime "heat maps" to see where the safest areas are. 

Was using the oven as a heating source

However, you as the owner have an obligation to make sure heat/hot water is working but all the while they can break things and making formal complaints about the condition of the home that will be documented against you.Unfortunately you will likely have to eat some sh*t pie and let them leave.

I used to work in the Pottstown/Reading areas and noticed those areas have a lot of houses that look similar and initially seem similar, but when you dig into the types of sewage systems, heating systems, and other major systems they can be very different (i.e. well water v.s. public water).

They quoted me $7,000 for a 3 ton w heat pump.

But you can't escape the value that comes from those non-quantifiable elements like experience, market knowledge, strength of your team, state of the market to ultimately determine Deal or No Deal. 

I work part time with my husband at his heating business.

Appliances with heating elements will use the most amperage (or current) meaning they run your electric bill up.

There are no deal on-market and if you are interested in this area, you would be wise to survey the market and get ready, but wait for the heat to cool off a little bit.