HVACPlumbing Electrical RoofStructure Any of these could be $0 to $30,000.Then flooring,  kitchen,  bathroom (s)$3500-$20,000 ,Each. 

Rehab consisted of complete gut renovation of kitchen/dining area, new hardwood floors and refreshed bathrooms (new vanity and paint).I am bullish about the long-term appreciation prospects of the property and have trouble envisioning the hold strategy over the next 10-15 years. 

Are there websites, that will giving me the current going rental rates for 2, 3  or 4 bedroom units in the different parts of Baltimore city Maryland?

If I could afford to I would renovate the bathrooms completely.

Do the same for cabinet hardware and bathroom fixtures.

I am in the process up updating kitchens/bathrooms in each unit and it will hit the 1% after that is complete. 

Now, investors can also buy on the high end and improve the home by adding a bathroom, taking a wall out and expanding a kitchen/living area, etc to be able to sell at a profit (a little harder idea to make profit but possible).  

For 20k in rehab you should have a new ac and furnace, hot water heater, updated plumbing, a new sink in the kitchen and bathroom, laminate flooring in the kitchen, new tile work in the bathroom, refinished floors, new ceiling fans, some light exterior work and some misc etc.

Among other things, I need to gut and redo the bathroom.

This BR already have a large walking closet and bathroom.