There are a lot of factors. In my area it usually takes 30-45 days. A cash sale for a vacant property that is not a short sale can be purchased VERY quickly. Inspections, re-inspections, appraisals, bank approvals, etc can make it slower.
As a buyer, you can assist the process by having your pre-approval (not just pre-qualification) ready. I have seen buyers waste weeks trying to find all the documentation that their lender requires.... more