Here is a link to a web site that has lots of good RV info including a per-purchase inspection checklist,
RV Inspection Checklist
As suggested earlier, you should get a RV tech to inspect the MH before you buy, but you can do it yourself first as well. You may find such an obvious deal killer that there is no reason to pay an RV tech to look further. It would be wise to negotiate your deal, then inspect. If you find things wrong with the RV you can re-negotiate or walk away.
Here's a link to another web site with useful information.
RV Basics .com - RV Information for RVers about RVing