Micro-small biz IT consultant here, who's supported entirely too many of these little boxes over the years. Take that as you will.

If you want to keep things as dead-simple and reliable as possible, a monochrome (black and white) laser is the way to go. Brother MFC-L2___ series for the lowest possible running cost. Canon MF4___ series for the simplest refilling and most consistent image quality over time (due to the combo cartridge -- toner and drum in the same consumable). Both are compatible with cheap third party toner cartridges (off Amazon or elsewhere), which can bring cost-per-page (CPP) down around 1c or even lower.

For Brother, I'd do an MFC-L2750DW ($281 - Amazon). For Canon, MF455dw ($269 - Best Buy). I'm personally partial to Canon, as they I think their paper handling and image quality is more reliable over time, and IMHO it's worth the slight premium on running cost for that assurance, but either one will perform well enough and I wouldn't fault you for going Brother, either.

Hope that helps. Any questions, feel free.