The area will be the primary deciding factor - you can renovate and modernize a building, but if you are in a bad area, you won't attract B tenants.

Our side is the same but one less room and half bath.The Redford home someone else had fixed up all new and modern.

You need to have the entire plumbing system scoped with a tv camera to determine the extent of the damage.I definitely would be budgeting both the time and money for a complete repipe and I would imagine rewiring the electrical system to modern standards since your going to have to gut the interior anyway.Offering a remodeled home with new plumbing and wiring as well as new interior paint and flooring will definitely increase the value and make the home easier to sell.

Google "Essex Modern City" for details and also "East Side Promise Zone".  

I've estimated the repair to be $20K -- just to modernize the property.

Yes sometime I just forget how computerized and modern we are on the West coast.

The place has been beautifully renovated by the current owner (downlights, new modern appliances, upscale bathrooms).

With bringing everything down to the studs and replacing insulation, drywall, wiring, and such the floorplan can be updated to a more modern style. 

My husband and I in the future plan to build modern, efficient SFH and multifamily housing. 

If you mean LLC vs Limited partnership, in general LLCs are considered more flexible and is a more modern structure.