We renovated our rowhouse room by room over the last few years. In my opinion $100k is a very low estimate or expectation to gut a house to the bones and rebuild. It’s obviously much more than just new walls and flooring. You’ll need new plumbing, electrical, fixtures,framing, insulation, finishing materials (trim work, doors, moulding, etc), potentially appliances, cabinets, HVAC, and more. Oh, not to mention the demo work and hauling of old material! You’ll also have the the expense of temporary housing and storage while the work is being done.
Consider refinishing the floors, if they’re salvageable. For your walls you can remove the plaster and lathe and put up new drywall. Or you could skimcoat the plaster walls if they’re in decent shape (they’ll look like new once they’re sanded and painted). The cheapest way might be to screw in 1/4″ or 1/2″ drywall over your existing plaster walls. The downside is you’ll lose a bit of sq ft but doing this. We did a combo of all of these where appropriate.
Best of luck!