We have never done that since the last two coached were purchased new. However I would imagine it would be buyers responsiblity since the buyer wants it. You might also be able to get a seller to pay as a condition of sale. A seller would wise to obtain a commitment to buy and price settlement based on a satisfactory inspectiion.
I agree with Ron (again). The buyer usually pays for the inspection. If you do have one done, make sure that ALL of the RV's systems are inspected, not just the running gear. Refrigerator, heating, a/c, microwave, etc.etc.etc.should be checked as well. As these homes run down the highway, EVERYTHING gets jostled around and you want to make sure everything is working correctly before you make that financial plunge.