From what I know it is acceptable after 12 months of credit in good standing. There are other qualifications besides this. To Learn more please visit http://www.fha.gov and you want to look for the "back to work" program or more importantly Mortgage letter 2013-26 This will give you the outline as to the qualifications. As Dan stated FHA says one thing but a lender may have other guide lines and may be more strict. If you should need anymore help, please feel free to contact me at your convenience.
Gillis and Company
A Division of ERA Key Realty
I work with the FHA back to work program.
Take a look at my recommendations here on Trulia from some of past clients here:
Please feel free to contact me for more information or help.
Senior Mortgage Banker
Peoples Bank & Trust