My family currently rents a 950 sq ft apartment and honestly, I'm just sick of barely scraping by so I'm going to stop treading water and begin doing something!

We are looking at a 30-unit built in the 1960's, and the current building is set up with two oil boilers, one for the hot water, and one for radiator heat.

Don't forget to account for vacancy, repairs, capital expenditures, property management (even if you self-manage, there will likely come a time when you don't want to), and water/sewer (if you pay for them). 

When it comes to a group of trailers aka mobile homes the big thing I see is waste water and sewage .

Myself I'd consider if it seemed like an area that has potential to change ..like if it's on the edge of a  hip or hot area or the city has plans to invest and revitalize the area .

These folks have caused a water damage and downstair roof has crashed down in the washer/dryer room.

Vacancy of 5% seems a bit low, I would use 7.5% (1 month per year) unless you are in a very hot rental market. 

When dealing with a shady handyman, that's like blood in the water for sharks.In the future, you can best prevent this by not waiting till the last minute to take care of such repairs. 

I am seeing that the market is very hot right now.

I agree with Michael that your main goal should be to determine if the property can generate a good positive cashflow after running the numbers and taking into account any cap X costs that may be coming up such as a new roof or hot water tank.