Bafang mid-drive motors are pretty reliable and relatively inexpensive and can be mounted to most bikes if you’re handy enough with tools. E-bikes go on sale pretty frequently because the market got oversaturated, but you’ll want to compare range, assist level, and ease of swapping batteries. The batteries themselves tend to be pretty expensive to replace and the extra torque can accelerate wear on your drivetrain components, but you probably won’t need to worry about that if all you’re doing is around-towning. I would recommend getting a regular (people call them “acoustic” for some incomprehensible reason) bike for yourself to start and consider converting later because you might end up enjoying the fitness benefits or the commute might be short enough that e-assist may not make much of a difference (if the office has a shower.

As far as what bike to get, you might want to keep an eye out for a used Surly or Soma, as these tend to be sturdy (if heavy) steel-framed bikes with mounts for fenders and a trunk rack, both of which I’d consider mandatory for commuting. You’ll want to figure out what sizes to look for based on height or (preferably) inseam measurements and do some test rides to see what sort of handlebar style you like (flat bar or drop bar) and how many gears you need (wider range gearing is useful if you have hills, less necessary if everything’s flat). I’d take a look at FB marketplace or Craigslist and post some of the ads you find for feedback; that’ll help you get a sense of what to look for and what to avoid.