I would rip up the worst areas of the particle board maybe all of it and replace it.

I roof here, a driveway there, an HVAC system there, a foundation repair elsewhere could eat through that easily.I would assess the condition of all major systems on each property and plan to have enough cash to replace each of them at the end of their useful life with some cushion for emergencies. 

Just remembered the Sheetrock was replaced on all the ceilings.

New stall shower install with garden tub replacement or retile (open to ideas at this point). 

We need to replace the HVAC system, and I believe this is a "B property". 1.

Then if you know of specific future capex expenditures, you can use inflation to forecast roof replacements, etc. in 5 years or whatever period makes sense for the property. 

Given the massive labor shortage going on, best of luck to him finding replacements.

rehab items- replacing flooring- painting walls- install 2 bathroom sink vanities- install 3 ceiling fans/ lightsAny input is appreciated,  thanks in advance!

We find that if your tenant is a sloppy pig and the rental unit is thrashed and a prospective tenant rents the unit in advance then that is not a good sign, at all, because prospective tenants that rent a unit that looks like a pig sty are also pigs.So, if the unit is filthy, then we don't show it to prospective tenants until after the current tenant moves and not until after we clean, paint replace carpets, etc..Obviously, the landlord's goal is to get a new tenant in the unit as fast as possible.

I just don't know if it is worth it.Is it likely I will recoup any investment to address some of the fundamental issues (raise sagging floors in the lower unit plus addressing issues that will cause in the upper unit when the walls raise 1-2", replace galvanized piping, re-do the poorly done roof) when we look to sell in 10-15 years?