After researching online I found landlord responsibility under California Civil Code section 1941 described as followsClean and sanitary buildings, grounds and appurtenances (for example, a garden or adetached garage) which are free from debris, filth, rubbish, garbage, rodents andvermin. 

- I haven't been able to find any 1031 opportunities (buildings or otherwise) to roll the money intoI appreciate learning your thoughts on whether to sell and keep.

You will need to learn how to run comps, figure out what rents are in the area and build connections to PM's, GC's, etc. 

The Columbus macroeconomics is booming due to many companies building out here like Intel, Meta, Google, Amazon, etc., and there is continuous population and job growth!

Quote from @Richie Linnon: I don't recommend small increases over a long period of time because it increases the chance of mistakes, it may still build animosity with the tenant, and the tenant may eventually reach a point where he can no longer afford the increases and he will leave.

The more relationships and marketing channels you build will only benefit you in the long run.

What strategies should I employ to build a professional network within the real estate community?

The reason those locks charge monthly is because there's an ongoing upkeep cost to maintain the software and communications network that are essential to being able to program the lock remotely.  

However I read books about real estate and thought that when I come to the USA, I'll start building my real estate portfolio, so here I am.I read several real estate books in the past, but now started to explore more while I'm in the USA.

If Jesus came back and got into rentals NO, N-O-B-O-D-Y get's admin access into our system. 2) They want a standardized list for maintenance items so they know in advance what repairs would cost.Being a PMc I'd invite them to acquire any of the readily available construction estimating tools/software out there such as RSMeans, but would not take on such a task as building and maintaining such a database, honestly for any $, it's simply not what we do. 3) They want a copy of all invoices from contractors to us so they can verify we are not marking up more than promised.A-ok. 4) They want to be able to talk to our contractors before work is done (each time) so they can talk contractors down in price themselves.I'd be fine with this as long as they sign a waiver that they own any/all negative impacts that result from such including extended vacancy periods, vendor refusals of service necessitating there own self-search to secure amicable vendor etc etc.. 5) They mentioned that they pay around $300 for full paint in a 2-bedroom unit.... we do not have a contractor that will touch a full paint on a 2 bedroom for $300LMAO!