Drilling and digging work by police and archaeologists started yesterday at the house in Station Road in Portslade, East Sussex, where the 63-year-old lived in the late 1980s.
Tobin is serving three life sentences for killing Angelika Kluk, Vicky Hamilton and Dinah McNicol but officers believe he may have killed many more and are searching the property for any remains or evidence.
Specialists are also scouring Tobin's former properties in Marine Parade, Brighton as part of the same operation.
Sussex Police started their investigations at the two addresses last Monday, convinced he claimed more victims as he lived across Britain under different names and trawled the motorways for vulnerable female hitch-hikers.
Tobin was told last December he would die in jail after he was convicted of strangling 18-year-old Miss McNicol.
The former church handyman was already serving life terms for the murders of 15-year-old Vicky and Angelika Kluk, 23.
Police discovered the remains of Vicky and Miss McNicol buried in the garden of a house in Margate, Kent, to which he moved in 1991.
The searches behind flats in Marine Parade and a hairdressing salon in Station Road, Portslade, could continue for a month.
The Station Road hairdressing salons were once a cafe, Ye Olde Tea-room, run by Tobin in 1988 with Cathy Wilson, who later became his wife and with whom he had a son.
Neighbours recall Tobin doing a substantial amount of DIY on the property as he converted it from a junk shop and cleared the garden.
The itinerant serial killer lived in several other towns and cities, including Glasgow, and Havant, Hampshire. Police said he may have owned more than 100 vehicles and used 40 aliases.