Having owned a similar one since 2004, I know a little about that model. Sorry for the length of this post, but I hope all of this is helpful. All of the info below is based upon my assumption that you are looking at a motorhome equipped the same as mine.
Overall, a real good, well built motorhome. It is probably on a Freightliner chassis, as I've never seen a 2000 model on the Monaco chassis. Freightliner is great in supporting their customers with a free 24/7 help desk. Monaco corp began using their own chassis for the Holiday Rambler line about 2001 best I can determine. If it is not a Freightliner Chassis, not a problem as I've heard the current owners of Monaco are still giving good support.
Tires: Came from factory with 255/80R22.5 load range G tires that were overloaded on the front left due to weight of slide. If you buy it, weigh first and upgrade tires if required. I'm running 275/70R22.5 load range H tires.
Leaks: look carefully for leaks around windshield (which can come from poorly caulked running lights above the windshield or a deteriorating top windshield seal. If slide locks are not used when slide is retracted, the top slide seal can leak slightly. Check floor along wall beside drivers seat for water damage. Look at that wall also. There are a lot of caulked joints along that side of the motorhome in front of the slide that can deteriorate and leak.
Roof: The roof construction is painted aluminum, and is very durable. Where the front and rear caps join the roof is taped along most of the joint, but not on the curved sides. These curved joints flex and frequently break the caulk causing minor leaks. (Marine 3M 5200 Adhesive Sealant will hold up here.)
Skylight in shower: check for any moisture between the two layers of plexiglass. Moisture indicates roof leak.
Roof vents: check for water damage around the roof vents.
Roof Air/Heat Pump Units: check for water damage around these units.
Windows: All windows except windshield are dual pane. Check for fogging between the glass, indicating broken seal. About $250 per window to have this repaired, or about $40 in materials if you do it yourself.
Slide: Probably a Power Gear - gear driven main slide. Check for smooth operation in both directions. The roller on the slide awning can cause minor noise during slide operation and is not a concern. With the slide extended, open the storage doors below the slide and verify that the slide motor mounts are still intact. Open the inside cabinet doors that are part of the slide and give it the sniff test. If it smells like mildew, the seal tape on the top of the slide is leaking and needs to be replaced.
Refrigerator: Check for operation, and for broken bottom door hinges. Due to weight of bottles stored on door and plastic door hinges, these often break.
Obviously, run all appliances, furnace, stove, microwave, etc. Put water in the fresh water tank and run the pump. Verify faucets and toilet work. Do the same using city water pressure.
The furnace has the 4 button thermostat that is troublesome. It is repairable but not replaceable. The upgrade is to a 5 button with a different wiring/control kit that is expensive. I've kept my old one going with periodic cleaning with contact cleaner. Check the operation of the thermostat.
Rear View Camera/Monitor: The factory unit is ok if it still works. It will be a black and white unit. Can be replaced fairly cheaply if you can do it yourself.
Televisions: Came with tube types that will not receive current digital signals without an external converter. Hopefully, these have been replaced with modern LCD units. If not, plan expenses accordingly.
If the unit has tile floor in kitchen and bathroom, check for cracked tiles. If tiles are cracked, see if spare tiles are still available in the coach (under bed or in storage bays). If you have spares, you can replace cracked ones. Try to determine what caused the crack, as mine experienced a cracked tile from the weight of the refrigerator.
Maintenance Records: Ask to review the maintenance records, and verify that the unit has had required service at decent intervals. If no maintenance records, you have no idea when the required service on the air dryer, transmission, engine, genset, etc. were performed.
The CAT 330 3126 engine and 6 speed transmission are very reliable. I've only changed fluids/filters in mine in 108000 miles.
On the chassis, check for worn bushings on the sway bars, track bars, shocks, etc. Probably best to have a diesel mechanic go over the running gear if possible.
Ask if the radiator/charge air cooler stack has been periodically cleaned. These require at least annual cleaning on rear radiator models to prevent overheating.
If you buy it you need to verify that the engine "slobber tube" has been extended to prevent oil fumes from adding to the radiator clogging.
That's all I can think of. If you have more questions, just ask here or private message.
Good luck with your purchase.
Fred
Fred & Vicki
St. Augustine, Florida
