If your current equipment inventory already includes an engraving machine and maybe a tabletop laser, and you are looking for a new income stream, it would be wise to check into ADA signage.
Take advantage of your current loyal awards and engraving customers. They likely include institutions like municipalities and public schools that all have to comply with ADA signage rules. You would be doing your customers a favor and potentially doubling the size of your business.
Braille supplies are readily available from your existing suppliers and most will answer any questions you may have to get you started.