I mean if I go that route then I would need to furnish the unit with a bed, shower curtains, pots, and pans maybe????

Anyway this shmuck I found online installed 2 toilets.

My next best idea is to replace some of the toilets, shower faucets, sinks, and washer with high efficiency items.Any help would be appreciated!

If you are looking at an area like that through the lens of a cash flow investors the numbers are probably never going to pan out for you.

In an apartment building, the landlord is responsible for the HVAC unit(s), roof, water heaters, toilets, exterior of the building, windows, common areas, landscaping, etc.

Bathrooms, toilet rooms, closets, halls, storage or utility spaces and similar areas are not considered habitable spaces.Habitable space requirementsCeiling height-RequirementsR305.1 Minimum height.Habitable space, hallways, bathrooms, toilet rooms, laundry rooms and portions of basements containing these spaces shall have a ceiling height of not less than 7 feet (2134 mm).Exceptions:1.For rooms with sloped ceilings, at least 50 percent of the required floor area of the room must have a ceiling height of at least 7 feet (2134 mm) and no portion of the required floor area may have a ceiling height of less than 5 feet (1524 mm).R304.4 Height effect on room area.Portions of a room with a sloping ceiling measuring less than 5 feet (1524 mm) or a furred ceiling measuring less than 7 feet (2134 mm) from the finished floor to the finished ceiling shall not be considered as contributing to the minimum required habitable area for that room.Floor space- RequirementsR304.1 Minimum area.Every dwelling unit shall have at least one habitable room that shall have not less than 120 square feet (11 m2) of gross floor area.R304.2 Other rooms.

If the problem is isolated to one fixture (sink, shower or toilet), it could be a local issue that could be fixed local to the fixture, but that is likely a short term fix as the other fixtures will continue to have low pressure as corrosion and scale build up.

That typically doesn't pan out in a residential zone (or at least not well enough for the headache in my opinion). 

The bathroom must have a 5' turning radius, the sink must be wall hung or open cabinet( 34" to top rim), the toilet must have the proper grab bars installed and at certain heights, the flush handle on the toilet must face the side that has the 5' turning radius not the opposite side.

Also, I added a "maintenance/repair" category for minor things like fixing a leaking toilet, broken window, etc.