The two that we did, we did basic stuff, nothing fancy. first one Fixed all the cracks in the drywall (did ourselves), updated vanities and toilets (ourselves), updated kitchen counters, cabinets were fine (contracted out) Painted Everything new, ceiling, trim, etc, correctly. spent hours and hours on the trim filling in the nail holes, etc. then contracted out flooring. Houses in the neighborhood were selling, but Slowly. (6 months), ours sold in a weekend priced higher than the others. right buyer, right time, done right.
The second we spent a lot more money on and made less, but still was a fun project. (redid cedar shingle siding. wife liked doing it, so okay, good). and then the similiar treatment above. It was in a more affluent location, so it would sell, but we actually did not do many things we wanted to. Outside perfect, 1st story was perfect, upstairs was tidied, but still dated. oh well, we walked away without a loss, and worried enough that we are not looking to do another unless it falls in our laps.
now my house, built in 1927, we just keep putting along doing what we need to, but waiting for the kids to move out, then we will gut and build it the way we want it.