Real estate sources tell TMZ the 'RHONY' star just privately listed her notorious 5 story Manhattan home and is looking to pocket $10 mil for the sale.

Also worth noting: this is at least her 7th time listing it, each time for about the same price.

If she can get someone to take the place off her hands, the buyer will score 5 beds, 7 baths and a ton of modern-day luxury -- like its own elevator, a sauna, gym and an irrigated terrace. Pretty good for a crib built in 1899.

We're told Sonja is looking to stay in New York -- specifically the Upper East Side -- but won't leave 'til someone bites. She's listing through Jordan Sachs of Bold New York.