A couple facts here.
A) The Texas Chain Saw Massacre is not based on a true story. It was loosely inspired by real events. Director Tobe Hooper spent his childhood in Wisconsin, where he heard stories about a local madman who murdered, robbed graves, and even made furniture from human remains. That man was Ed Gein, indeed a real person, but that's where the film's connections to reality end. If there was ever a chainsaw-wielding serial killer who stalked and ate hippies in Central Texas, it is not public record.
B) You'll be happy to know that the actual Chain Saw house is very much open to the public. You can even catch a bite there (!), as it is now the Grand Central Cafe in Kingsland, TX. That humble cafe is housed in the original structure where Marilyn Burns and Edwin Neal and Gunnar Hansen spent a miserable summer in 1973 making motion picture history. This house--The Hewitt House--was used to film Michael Bay's 2003 remake. So while its history is fascinating, its pop cultural value is dubious. It certainly isn't worth a trespassing charge. Hope this is helpful.