Upvote:2
Usually applicants for a Schengen visa have to document the source of their funds, which is not quite the same as having a sponsor. They also have to demonstrate why they would leave again.
In Germany, there is the option of formal sponsorship for a visitor visa in the form of a VerpflichtungserklΓ€rung, a document where the sponsor guarantees to reimburse the German state for any costs should there be an overstay. Most visitors get their visa without a VerpflichtungserklΓ€rung, but it can make the difference in cases which would otherwise be denied. To make such a formal declaration, one has to be a resident and earn enough to cover likely costs.
And there might be the possibility of declaring your mother your dependent. That's difficult, and Expatriates Stack Exchange is a better place to ask.