Consular policies vary, but it's important to understand that what they are mostly interested in are ability of the traveller to support themselves and reasonable assurance that they will leave the US and return.
The first one is fairly straight-forward (normally proof of funds or/and affidavid of support from the inviting party will do), the second is a little trickier. Answering your question, property ownership is not at all necessary ;basically it helps to prove established ties with the place of permanent residence - things like steady job, family ties, any long-standing and binding contracts (rent, mortgage etc). Property ownership certainly helps, although no strict criteria exists.
Good luck
