When you reno a unit, it is tempting to gut the whole thing and do it to "your" standards...say move a wall for a more open layout with better flow. While in certain circumstances this may be desirable (eg to correct a big problem with the unit and add value) generally this may not be such a good plan.
When you do this you get into the "where do I stop" cycle...you tear down that wall for better flow, then find the knob and tube wiring, or galvanized water lines, then you see the lack of insulation where the removed wall joined the outside wall, or maybe you started the plaster to loosen on the ceiling, or discoved the uneven subfloor, or you find the hidden asbestos in the HVAC, or discoved that non-load bearing wall had some point load, etc, etc, etc... Best case scenario, you will have to patch, re-floor, and paint.
Unless you are already planning a big reno or gut job with flooring, painting, etc., I would recommend keeping the original layout.
The best moneymakers are the properties needing only clean-up and paint anyways. A gutted house brings in no rents! Besides, are you a contractor or a real estate investor? You have to ask yourself how much more rent will the reno bring in? I like fixin' houses, but not so much that I do it for free!
Renos are like onions...the more layers you take off, the more you want to cry!