How much does it cost to file a patition to partition

Attorneys are not going to answer your question in a forum like this.  You need to contact an attorney directly for that type of information. The fee would depend on yours and your brother's locations, the value of the property, and how much equity your mother had in it. Since it is impossible to tell whether this will take a long time to resolve or whether your brother will be reasonable and agree to sell the property privately once he realizes how much equity is going to be eaten up by the litigation, most attorneys would start off with a fairly modest retainer fee and then work on an hourly basis after that. You need to look for an attorney who is both experienced in real estate (like me) and also litigation (like me).  Many real estate attorneys only handle transactions, and are uncomfortable in a courtroom (unlike me).  Good luck.