You will be lucky to get 20 years out of kitchen at STR quality and should maybe plan for 15 years.  

Could be a new roof, HVAC system, or new kitchen along the way (all of which could certainly add equity to the home irrespective of the year it was built).  

I ask because if you redid ele and plumbing for kitchen and bath, plus added new panel and did rewiring, than those costs are quite low.

Upgraded kitchens, bathrooms, and other items that hadn't been touched for years What was the outcome?

After the tenant moved in the repair calls starting coming in 9 times in 12 months - backdoor was stuck again (that was part of minor repairs), heat went out, AC not cooling, kitchen sink leaking,  etc.

The kitchen looks extremely small from the pictures.

the kitchen,fridge and bathrooms are disgusting and it is damaging the properties.

Purchase price: $179,000 Cash invested: $15,000 Lived in the property for 1 year.Knocked down living room wall, replaced Hvac, floors and gutted and remodeled the kitchen, attic insulation, converted the living room and the dining area into rooms.

We even made little signs to go up on the. door and on the kitchen to warn about fraud since it is more likely with self-guided showings.

She had issues with her kitchen faucet leaking.