Even if it were new, they have no idea about the quality or manufacturing imperfections. 

There's certainly other aspects that you need to consider such as pricing, quality of photos & overall listing, is it clean/repairs are done, if there's tenants are they being decent to people during showings, are you requirements reasonable etc... 

Some contractors have insurance, some are 1 man band with no overhead, quality of work factors into cost, level of finishes.We created a calculator for our clients to use here in Chicago, specific to our renovation pricing, but even that is just a guess based on some assumptions.If you can find a quality general contractor, pay them like @Bruce Woodruff mentioned, and it will make your life so much easier...you may eat into some of your profits, but being able to rinse and repeat with someone you trust is priceless!

Managing contractors and verifying quality of work/timelines can kill a deal.

Are their listings detailed with good-quality photos?

I tend to favor buying a few high quality properties in  coastal CA (Bay Area, LA, San Diego) over buying lots of less expensive properties in other states. 

This one is/was a C- or worse at the beginning and now they would be about a B quality buildings in a Cish neighborhood.

This one is/was a C- or worse at the beginning and now they would be about a B quality buildings in a Cish neighborhood.

I definitely recommend that you seek out a Certified Cost Segregation Professional so that you are confident in the quality of the work performed and the deliverables produced.

As long as you have reasonable expectations of:- Running a 24 hour business (mostly remote but guest communications and emergency maintenance issues)- Managing cleaners (schedule and quality)- Managing maintenance (urgent and scheduled/preventative)You will be fine.  80% of the work is remote, with the exception being cleaning and maintenance.