Mike
I bought a drill press add on mortiser years ago and could never get it to stay on my drill press since then I have met a good number of folks that have had good success with them.I have a floor model mortiser that does a reasonable job although I don’t recommend the company who made it. if you’re going the mortiser route you might bump your budget a bit and go for the powermatic even though I’ve had good luck with grizzly products the powermatic has better reveiws.

https://www.amazon.com/Powermatic-1791310-PM701-Horsepower-Mortiser/dp/B000BX1JQU/ref=sr_1_2?ie=UTF8&qid=1471632821&sr=8-2&keywords=mortiser+machine

woodworking classes, custom furniture maker