Btw, this is the budget DIY… if it’s in a large area or house wide, look up rental rates for heaters and fans. Need to provide continuous heat above 120F for a few hours.

Diatomaceous earth and heat treatment. Washed and dried linens/clothing on high heat and bought a steam mop to steam/heat every square inch of carpet or mattress. Spread diatomaceous earth cautiously and do in a well ventilated area wearing a mask or respirator.
Worked when I discovered bed bugs in my guest room after I had a friend stay with us for a few days. I check religiously now and haven’t seen any since my treatment two years ago.