I am picking up a new 5th wheel at the manufacturer. How much insepction can you do like checking the appliances and power outlets, propane & water systems for leaks, etc. or do they just tell you to drag this thing of their lot. What are the most important things to check?
Absolutely essential is anything involved with hitching up and towing it. Suspension, tires, brakes, hookup cable, landing legs, stabilizing jacks, trailer wiring, stop lights and turn signals.
Slides, if any. Run em in and out several times, and check the seals when they are out.
If possible, check all appliances, even the ones you don't need right away (ie, both A/C and heater). Gas powered ones may be a problem, but you not only want to verify working of all water and electric fixtures, you are even more interested in spotting leaks/shorts.
General walk through to spot anything obviously wrong.
Personally, I'd try for living in it a day or 2 before leaving or even finalizing the sale. That's how we found that the toilet leaked whenever you sat on it.
It is much easier to get something fixed before you leave the lot, than after...
Try to do the ole complete walkthru and have the salesman/etc., do a complete check for you on how "everything" works (*including hot water startup (with water in tank), fridge, A/C, slides, etc). They have (bigger RV dealers) have connections in a location where they can hook stuff up the night before you get there to pick it up, so you will be able to see that stuff actually is working. Once you leave the lot, it is a real hassle to get warranty work scheduled inbetween normal work and warranty work for all folks. Do it up front is my saying before you leave the lot.......some even have an attached campground to stay at to check out the stuff.