My brother repeatedly told me he didn't make much money mowing lawns. He used John Deere residential mowers and did none of his own maintenance.
There's the problem, I can set aside what I believe to be an overpriced brand however I can't let go of not doing your own maintenance.
That's just a huge money sink, in addition to doing all of my own maintenance I also procure pretty much all my own parts (this isn't as easy as it sounds).
Probably best to take it all one day at a time.
It took me years of shopping around and twiddling with the wrenches to become intimately familiar with the mowers and the parts.
It also takes quite some time to get all the tools needed, best here to start with the basics and expand from there, slowly, methodically.
Brand loyalty has been a big help, most of my earlier mowers are Toros, then came a couple different brand Z's and later I got into Honda 21's but between that and the Stihl hand helds...
The only 'residential' grade mowers I have are the 21" Hondas, I don't use them but in backyards where the gate is too small...
The 10-gauge deck on the Flatlander concerns me as well however Dixie Chopper does claim that Ztr to be commercial grade...
Everything else I run are commercial grade Toro mowers with 7-gauge steel decks and frames.
Brand loyalty helps considerably in terms of cross-referencing, parts and trouble-shooting, so for now you may wish to stick to the JD's but more than anything I would suggest becoming intimately familiar with the machines.
Then, start learning how to service them and where to acquire the parts.
For further reference a 7 gauge deck and frame is made of 3/16" thick steel, they are extremely durable.
10 gauge decks are made of 9/64" thick steel, this is much thinner and bends far easier.
That is one of the biggest reasons residential mowers are cheaper, steel is very expensive when you get into stuff that's nearly a quarter of an inch thick.
I've hit solid obstacles at top speeds of 7-10 mph and 7-gauge never dents or cracks (actually once in 16 years it did bend a piece).
You might say I should be more careful but it's not your own lawn you'll be mowing.
Time is money and obstacles can appear suddenly in thick grass, bending a deck is an expensive parts and labor-intensive proposition.
Why I pay careful attention to the thickness of the steel that the deck and frame are made out of.
https://www.tedpella.com/company_html/gauge.htm
I became self-employed in 2001