That depends... as long as both parties agree there is not set number. If asking for an extension try to do so when you first find out you need one so all parties are aware of the situation and can plan accordingly. Neither party has to extend so if you do need to extend make sure you clearly explain the circumstances of why the extension is needed and when you plan on being able to close.
Hope this helps.
Don Groff | REALTORÂ® & Mortgage Broker
Austin Real Estate Pros & 360 Lending Group
o 512.669.5599 | m 512.633.4157 | firstname.lastname@example.org