I ended up with a 2022 MM 2100 Bhs, non Flex, but looked at several Flx and Non-Flex units. Mine had gone to the coast a few times so there was likely more surface corrosion because of that, and below describes the poor weather protection of some of the outside wiring, you might want to look at.
Make sure you hook it up to water and run all the water, Winnebago did a cheap job with their plumbing mixing pex, and flexible lines with pex clamps that can eventually leak.
You can likely view,(I think common on all MM's) from above on the driver side of trailer, inside the front tongue area is a poorly weather protected group of 4 auto reset breakers. Just observe how corroded they are. There are easy to remove little red rubber breaker covers, you can pop off to see connections. My unit had a lot of corrosion on the connections, but fairly easy to get to. There is a 30 amp blade fuse nearby breakers poorly weather protected, that was also corroded but easily replaced that runs to the electric jack. There is a electrical junction box further underneath and behind breaker strip that is better placed out of direct weather, no exposed connections, but incredibly Winnebago put a residential metal junction box in, for outside use, which was corroded on the outside. Guessing that is common to all MM's but you have to crawl under to see. Even with outside corrosion the interior wires were fine. I've since installed weather proof boxes for both breakers and junction box.
Run the slide in and out several times observe for straight in and out running, odd noises, pops, check outside slide seals, and observe moving outside if you can while connected to shore power. My slide worked fine, but worth checking operation thoroughly. On the Flx, before arriving, install a Lithionics phone app to check the charge status, and I believe use, and health of the blue tooth capable battery, which I was told is also a Winnebago owned company. I believe the Xantrex inverter may have a phone app utility too, but also has an onboard status display as I recall. Great little trailers, would be even better if Wall St bean counters weren't running these companies.
