Kenneth Jolly, from Forfar, was remanded in custody after a jury at the High Court in Perth found him guilty of raping one prostitute and sexually assaulting three others over a nine-month period between October 2010 and May 2011.
The 54-year-old trawled the streets for prostitutes to take to his caravan in Bridgefoot, near Dundee.
Presiding judge Lord Boyd paid tribute to the "courage and dignity" of the victims who came forward to give evidence against Jolly, who will be sentenced at the High Court in Aberdeen on January 14.
Jolly was also placed on the sex offenders register and the judge ordered a risk assessment report to establish whether he would continue to pose a danger to women.
The trial heard how Jolly had picked up women on the streets of Dundee and agreed to pay them for sex before taking them to the caravan park.
But after they stripped to have sex Jolly would turn violent. Jolly claimed the women had agreed to all of the sex acts which took place in his caravan.