Juan:
1. No I was not thinking of a telescoping boom unit but rather a vertical lift masted fork lift - like Case, Ingersoll Rand, etc If you are think of an indsutrial pneuamtic tire forklift fro your needs one a 5k unit which will have ~ 5 underclearance at the mast with new tires migh work for you but these units in teh used market are relativelyley hard to find (ie a decent one) so the price will be higher than your budget adn teh unit will weigh more than the 10K limit of your trailer ~12K to 12.5k range
2. Hourmeters are readlily replaceable items on forklift so unless you know the history of the unit you can be mislead. Hourmeers can stop working or be disconnected as well. A good inspection by a knoweldgeable person can give a good estimiation meter is accurate - they look for wear on the upright, channel sections, excess play in the steering system (axles, etc, looseness in the mast mounting, tilt cylinder mast racking, signs of abuse, engine smoke, transmission slippage or harsh engagement etc etc. Most hourmeters have a 1/10 of hour digit or a wheel that indexes arpound when the ignition key is on - turn the key on on and what to to see if teh 1/10 digit advance or the wheel indexes - on some makes the hourmeter will only operate when the operator is in the seat.
3. Remeber at an auction all sales are "as is" and final once you pay. Have seen many customers that bought a unit at an auction or on the internet and were not real happy when they got it home.