In general, legal fees you pay to obtain business income would be reported when paid, even if the income was not paid until later, or not at all. For example, if you have a rental house and you sue a tenant, that would be a deductible expense when you pay the lawyer (or the court filing fees, etc.) even if you don't recover the missing rent until the next year. (Your legal fees would generally be deductible even if you lose the case.).
"Investment property" can mean many things. If you bought vacant land hoping you could sell it later for a big profit, then you have no ongoing income to deduct legal expenses against. Your carrying expenses (like property taxes) would be miscellaneous itemized deductions subject to the 2% rule, except that was eliminated in the 2018 tax reform law. You might be able to capitalize your expenses, except that the capitalization rules are tied up with the elimination of the miscellaneous itemized deduction and the effects are not clear.
I am also unclear on why you are receiving money. Did you sell your interest to your partner? That's a whole different kind of tax issue. Legal fees to establish clear title in order to sell property are an adjustment to basis, not a deductible expense.
Partnerships can certainly be more complicated, and up until the partnership was dissolved, you probably should have been filing a partnership return in most cases (and if you didn't, that might affect your tax position now).
I agree that professional advice specific to your case would be recommended.
