Re: Partition Action- Joint tenant
First, about the abandonment thing. I believe you are referring th adverse possession, sometimes called "squatters' rights." In many cases, someone who occupies property owned by another for five years will acquire title. This requires that the possession be without permission and that the adverse possessor pay all the taxes. Adverse possession by a co-owner rarely happens, for the simple reason that the possession of a co-owner is by right and therefore isn't adverse. There is an exception where one co-owner is more or less kicked out; this is called an "ouster," and after an ouster of one co-owner by the other, the possession bcomes hostile and adverse, and after five years the title of the co-owner out of possession can be lost. This doesn't happen very often, and if your mom left under peaceable conditions and said that she might return at any time, there would be no ouster.
Next, as to what a lawyer would cost. The last partition I handled was more or less typical, and as I recall the client's fees and all costs came to about $15,000. My rate tends to be on the low side, and I will sometimes accept partition cases on a deferred fee basis until the property is sold.
In addition, many partition cases settle soon after the partition lawsuit is filed and served, because the co-owner wakes up and decides to negotiate for a private sale and out of court split of the money, rather than endure the litigation, which almost always ends up with a sale of the property because there are few defenses to a partition suit.
One result of a partition is that your mom would be entitled to reimbursement from the net proceeds of sale for all of her excess outlays for mortgage payments, taxes, insurance, necessary repairs and the like, before the balance was divided.
Further the proportions in which the purchase money were put up might determine the percentage ownership upon sale. For example, if you mom paid 75% of the purchase money (down payment and closing costs), she could very well be legally entitled to get 75% of the net proceeds of sale.
Finally, I should probably inquire whether you mean a business partnership when you use the word "partnership." More likely, you mean a living-together arrangement of some kind. If this were truly a business partnership, where you mom and the boyfriend bought the property with making and splitting a profit as the primary goal, some different law would apply to some aspects of the situation.
Please feel free, either of you, to contact me with details for a no-cost evaluation of your case.