If you get a Freightliner chassis, you will be going to a Freightliner dealer for everything but the house stuff. I get my oil changes at Speedo but have the rest of the work done at my local Freightliner dealer.
Both Cat and Cummins make a good engine. I have a Cat C7 and it works great.
You should not have to replace the brakes unless you do a LOT of driving. My exhaust brake does most of the work.
You did not say how old a coach you were looking at. If you cannot get maintenance records, I would change the main belts, fluids including radiator fluid. If you are purchasing a Freightliner chassis, I have a maintenance spreadsheet that lists all the maintenance items and when they should be done. I will send it to you if you send me a PM with your email in it. I cannot attach a spreadsheet to messages on this forum.
You will change the tires at about 7 years. You will not put enough miles on the tires to worry about how many miles they have on them.
I have a 2004 coach and this jacks and stairs are working fine (knock on wood) so I cannot say how long they will last.
