It must meet the requirements per the building code IRC (I think Massachusetts follows a modified version of the IRC) you must provide the required amount of light, air/ vent, and egress.

(I live in Buenos Aires, Argentina)...  

I'd probably replace it with the same flooring as the bedroom for a cleaner & updated look.

This property is 10 minutes from the University of Riverside and 20 minutes from March Air Reserve Base.

Our cleaner had to spend 10 hours to clean the whole house!

It seems to be the most sensible option given for us that our cost basis for the rehab is very up in the air.

For example:General-Filters (furnace, air conditioning, oven exhaust, refrigerator, and water)-Stove burner when the “eye” needs simple replacement-Batteries and remotes that service the premises-Fan and light pull strings-Smoke and carbon alarms testing and batteries-Ensuring appliances are properly plugged in, hooked up, and used-Removing dirt, debris, and lint in and from connection pipes (e.g. clothes dryer)-Tighten loose screws on all home functions (e.g. doors, hinges, handles, socket -Balancing off-balance appliances-Cable, internet, and phone jacks-Fire extinguishers-Systems operation (e.g. security, irrigation, HVAC)HVAC-Monthly A/C filter and drain line maintenance Electrical-Reset “tripped” GFI breakers-Light bulbs (throughout and at the end of the tenancy)-Blown fuses-Reset breakers in the outside and inside breaker boxes-Socket and plug outlet coversPlumbing-Unclog drains or toilets-Caulking around tubs and showers as needed-Gas pilot lighting-Leaky faucets and shower heads-Toilet flappers, handles, seats and seat lids, tank lid, and flush kit-Sink and tub stoppers-If septic tank present, use RID-X as directed on consumer box-Proper cleaning of garbage disposal-Loose faucets and sprayer heads and hoses-Faucet filters (i.e. aerator)-Open exterior plumbing clean out when necessary (e.g. sewage backup)Exterior-Routine lawn (and pool) maintenance-Adjusting sprinkler heads as necessary-On the last month of tenancy, tenant must perform required lawn maintenance no sooner than 2 days prior to vacate dateThere’s a lot to consider as a landlord.

As well as doing annual inspections on HVAC systems, make sure detectors are working properly, air filters are changed and just to make sure the tenant is taking care of the property? 

I do the same for cleaners, if it’s extra cleaning charge for greasy kitchen or dirty tubs etc., then have it itemized and charge those amounts that are over and above normal.

Who are you using for cleaners?