Replace all TCs, drain water, add chemicals in all toilets to kill roots in the system.

Heat and chemical.

The pest company should take on treatment for termites, framing work, and anything that requires chemical treatment. 

Please make sure you or workers wear cartridge style air respirator when removing that carpet and spraying with any of these strong chemicals also probably should wear a white tyvek style suit etc. 

Septic companies around here dont clean drainfield lines , they just replace ( around $ 20K with the new systems ) So I am figuring on about 200 bucks in stone and 80 dollars in fittings and 100 in chemicals .

I spray the leaves with Round-up on a warm dry day (normally wouldn't use it, but sometimes chemicals are your friend), then plan to go out in a day or two and remove as much as possible.  

We have a dog and cat that have brought fleas into the house and instead of using harsh chemicals, we spray this on the animals and floor, furniture and carpet.

We remodeled the house, fixed it up, had it treated for termites, and then made it into one of my best rentals...but of course the story doesn't end there.We treated the wood but the chemical today used isn't like it was years ago.

BTW, if they are dirt bags, criminals or cookin up a new batch of chemicals, they won't ever open the door. 

Train derailed 3 miles away carrying some hazardous chemical etc.