Some other thoughts. Set alerts on craigslist for units of all types. A small industrial unit is best and the most durable. My brother scored a 10kw nat gas 220v unit on CL. for $2,000. I know you said liquid cooled but I have bought old RV’s for peanuts. Salvaged the generator and sold off the parts and made a profit.
Also, my neighbor has a Kohler stationary that gets test run every week for three hours. It works every time for several years. Just saying.