When we think of street-level apartments as basements, those negative connotations come mostly from water damage: mold and musty smells, flooding and insects attracted to water. The garden-level home for you must be designed -- or redesigned -- with these concerns in mind.
First, look at the street outside: Are the gutters wide and capable of draining off even excessive floodwaters? Are the edges of the street curved down, so water doesn't collect in puddles? Are there any signs of recent damage, or renovation, to indicate the level of regular maintenance to expect over the coming years?
Inside, be wary of obvious signs of damage and decay. But also look for fast, cheap solutions to lingering problems, such as new drywall patches and panels, slapped-on paint and other indications of quick fixes that haven't necessarily treated the underlying issues.