I had this exact same problem. I purchased a really run down park with homes that needed to go to trailer heaven. The tenants were poorly chosen and often had run ins with the police.
Shortly after purchasing the park I found out the seller was harassing the tenants and pitting them against me. Worse yet, this guy was well known in the community for bullying people to get what he wanted. The tenants had been bullied so much by him they were afraid to stand up to him and believed every lie he told them about me.
The park was owner financed through a bond for deed agreement and I was afraid he would foreclose on me. I consulted with an attorney and here is what I found out.
If you have a legal bond for deed and you have proof of your payments he can’t legally pull the deed. It’s pretty iron clad. One thing to remember is, according to the attorney, the property belongs to the seller until final payment so unless it is in the contract you really can’t make changes unless the seller ok’s it in writing.
Try to work things out with the seller (judges are usually favorable to people who try to work it out on their own). To quell the harassment I would call the seller when he pulled a stunt. Turned out he was just a big bully that when I called him with a calm but firm voice he would back down every time. I also became more visible to the current tenants and evicted the worst ones as quickly as possible. In Louisiana the lease agreement is null and void when the property changes hands so it was a simple process of giving tenants notice and getting them out.
Document EVERYTHING I hope you don’t end up in court but if you do you need to show that you tried to resolve the issues by methods that are ethical and legal.
Lastly, I worked on getting a loan for the park ASAP. The day I bought that seller out was the best day of my life. He even offered to sell me another one of his parks at closing.