Apart from not being too wide, too narrow, or having the correct number of spoke holes, you must consider the angle that the spoke holes in the rim are drilled at. The spoke holes on any specific rim are purposefully drilled at angles to allow the spokes to be laced at the correct angles for the application.
Spoke holes for a disk brake will be drilled at less drastic angles than those of a rim drilled for a drum brake hub, as the drum hub will be much larger in diameter. Take a look at your rims and compare them to the photos of that eBay rim, you will see similarities or differences in the spoke hole angles.
Also ask the seller's opinion, he may have some expertise to share.