1. Based on your expected usage - stay away from electric.
2. Auctions can be a good place to buy one economically but can be expensive to own. The are sold "As Is Where Is" You have no chance to try it in your operation. When a forklift dealer buys used equipment (meaning a 5k, Lpg, indoor unit) from auctions or off lease equipment they expect to invest and additional $1900 to 2500 to make it retail ready. You generally can buy the unit from a dealer with various types of warranty - from As Is but rental ready, 30 day, 60 day, 90 day, with warranties covering "bumper to bumper, drive train only. Of course the more comprehensive the coverage the higher the price. Plus, through a dealer you finance-to- own a unit. Age, make, model of the machine may affect the finance that is available.

3. Generally, with a unit coming out of a "normal & clean" operation, one can expect the unit to run 8000 to 10,000 hrs. Before extensive repairs can be expected.
Don't fall in love with low hour meter reading for the following reason - hour meters can fail and be replaced, hour meters can be replaced, hour meters can be disconnected, the hour meter stopped working & never fixed, etc. Have someone technically knowledgeable of lift trucks look over the machine to make certain some one is playing the "shell game" on you, like low hours but excessive steer axle play, worn mast channels, etc.
Most anyone can make a POS look and run like a top for a short period.

I'm certain there are other things - you mentioned abuse - a lift truck can be abused many, many different ways - some very creative too.