Parents considering MH retirement community

[rb]

My folks are considering selling their home and buying a MH in a retirement community. I don't know anything about pricing on these homes, and want to make sure that they don't get into a bad situation. Where can I go to find out:

1) pricing on MHs - I want to make sure the price being asked is a good value (it seems high to me)

2) information about retirement communities that lease the lot for your MH. What are the potential pitfalls, is there a place where these service providers are rated or evaluated.

Thanks for your help!