The government-backed mortgage giant Fannie Mae mae.com has raised the ante for lenders wanting to do business with it.

Fannie Mae issued a new selling guide last week detailing revised eligibility requirements for companies looking to both sell Fannie residential first mortgages and service those held by the GSE.

Lenders now have to prove a net worth of at least $2.5 million, plus a dollar amount that represents 0.25 percent of the outstanding principal balance of any Fannie Mae portfolio it services.

A lender’s Fannie Mae portfolio includes mortgages or participation interests in mortgage-backed securities (MBS) pools, first and second whole mortgages held in Fannie Mae’s portfolio, Fannie Mae’s participation interests in first or second mortgages in participation pools held in its portfolio, and multifamily mortgages, the GSE said in its selling guide.

Previously, the requirements stipulated that lenders have a net worth of at least $250,000, with additional cash on hand equal to 0.20 percent of the portfolio.

For those doing the math, that’s a ten-times increase – a big enough bump to suggest that some smaller-sized companies could be cut out of the GSE’s business.