Do yourself a big favor before you buy. Make sure you know what you're getting into. If the house has a crawl space then be sure that someone has a look at it specifically for mold growth, standing water, condensation (especially on cold surfaces during the summer months) and opportunities for humid air and/or water to penetrate though outside openings and ground moisture to enter via gaps or tears in the vapor barrier (if one even exists).
The presence of mold or moisture issues in an otherwise structurally sound house is not necessarily a deal-breaker as in many cases these can be effectively resolved by experts in the waterproofing/moisture control and remediation fields, but knowledge is power - and in the case of a prospective home buyer such power can be a valuable negotiating tool if you still desire to purchase the property.
Have a look at this article for more information and tips: http://aspenenvironmentalservices.com/mold-hiding-home-buying/