In either case, provided there is not too much texture, you could remove the doors, and, perhaps, the boxes as well, and {spray} paint them {primer and finish coat(s)} and change the hardware to give a more modern look.

That guy told him that the heat treatment is the best, because you can't "miss" an area when applying it (like you can with spraying chemicals), it's just universally applied throughout the dwelling and spells death for the bugs, no re-treatment needed.

At the very least carry pepper spray/mase.Safety should always be a concern and should never be taken lightly. 

Within a few days of moving in they were being bitten and eventually brought in a live bug in a jar.

Jarred I enjoyed your post and like all television it's there to entertain...HGTV, DIY and Live Well are just a few that happen to educate also.

Not spraying the ceiling or trim.

You can then have he/she run the calcs and plug in an upgraded type of insulation to say spray foam for example.

But the tenant was prone to using spray chlorine & one of those green scrubbing pads to clean the counter tops & the use of a cutting board would have helped prevent compromising the surface.

The area is lower class neighborhood,  however,  all the surrounding homes have really nice gardens and grass.Not sure if any kind of spray was used by the tenants to kill the grass.

Try reaching out to @Jarred Sleeth