Do payments received from the rental property count as a combined income?

First things first. If you are in a divorce and own significant property, you need an experienced family law attorney. It's almost always worth the expense. Second, equitable property division is not mechanical. The two spouse since they calm down can usually divide their property a lot better than a judge who has been watching two nice people flinging mud at each other can do. The answer to your question assuming the two spouses are not mature enough to compromise and work things out with each other requires more information about the source of the original money; what the size of the other spouse's contribution has been, etc. So it is not easily answered. But you and spouse can provide your own answer if you try. Good Luck.