The previous owners did a poor plumbing job and it all that had to go.

If there is actually water left after the cycle, you may have a plumbing issue but doubtful.

I believe they were telling me it was a plumbing leak going into the basement from the ceiling. 

I think the unit can get changed before things freeze up... unlike Patrick's story where it was a new heating system that takes more time/plumbing, and it sounds like there were not tenants there to give him early warning.NOTE: Extending the life of something that has cosmetic effect like paint, will cause the quality of tenants to waver... and it could be a downward spiral... so keep the place looking nice.  

So when I have to fix a plumbing issue say $300. 

Maybe you could work a summer for a contractor and learn some basics of the trades (carpentry, plumbing, etc).

With that in mind, we believe that the following work is absolutely necessary:• Demolish and rebuild garage: $41,952• Plumbing repair & update: $9,896• Electrical repair & update: $12,343• Foundation and structural repairs: $30,135Total: $94,326This is a significant amount for us to pay, and we are hesitating with continue on with the property as priced.

Let me drag this out with an elaborate example: Let's say, theoretically, I decide I will do all the plumbing, electrical, and finish work myself.

The majority of the work will be plumbing and sewer for the new kitchen. 

They negotiate better than market rates for flooring, plumbing and pro services, but the handyman rates may run higher than the open market since they only use licensed and bonded workers.