yes make sure everything is in a contract, even that can not prevent some issues.
I once purchased another web hosting company that had clients and everything looked fine.
so took over the business, then noticed that what some of his clients were paying was low and even some hosting for free. It seems these were family and friends. so i naturally emailed them introducing myself and saying that i will be looking at their plans and usage and then create paid plans for them. then the person who sold me contacted me to say ' why are you going to charge **** these are my family and friends and i gave them free hosting' my reply was so what you sold me your business, so you have no say and as these have no ties to me then they will need to pay like any other client. I only lost 10% of these free clients when i presented them with a charged plan, but the worse was to come. I kept open the emails the seller had created ( changed passwords so he could not access them) and i got an email threatening me with legal action if i continued to use the site template as it had not been paid for. I told him i took over the company and as the invoice is in the name of a limited company then he has to chase that limited company which i never took over or any association with. i then just removed that email address and then changed the site template