There are limits to extra income -
[While a disabled (nonblind) person applying for or receiving SSDI cannot earn more than $1,070 per month by working, a person collecting SSDI can have any amount of income from investments, interest, or a spouse's income.]
http://www.disabilitysecrets.com/res...-ssdi-benefits


I guess it might depend if your Ebay sales are run as side business of some sort, but it is a traceable influx of money..

Others might be more in the know..on the details ..