can't be just lighting for the hallways/exteriors for two buildings.

I may end up doing a little painting on the exterior, but any expense would be minimal.

Same procedure for boiler/heating system but perform a separate test on this.Usually the elbows in runs near the exterior walls break first which actually reliefs other parts of system.I have seen freeze ups where it was only minor a few elbows here and there.It really needs to be done on a case by case basis but it seems like your preparedfor the worst but I don't think it will be that bad. 

I had the same issue in my SFR and was advised to grade the space so that the water would drain out along the foundation to the exterior. 

@Russell BrazilBased on recent experience with investor buyers I see the market for rentals tightening in some of the nice bread-and-butter neighborhoods (as opposed to the red-hot ones near the water).

Interior or exterior.  

I would hesitate to lock up HELOC funds in a buy and hold also unless you are absolutely opposed to doing some sort of cash out deal, either flip a property or BRRRR.

Indoor I have cleaned area(if non structural) applied either wood filler or mud with plaster to harden, sand to flush, then prime and paint.Same thing for exterior non structural areas of smaller size. 

Just my preference.Definitely go for sliding glass exterior doors! 

The returns are not that great and I'm not opposed to selling.