A 13 percent yield I don't trust, against 40k of business reserve

You already answered your own question in the third paragraph. The dividend and the price move are the same number seen from two sides, so add them together before you call it a return. Twelve down to nine is minus 25 percent of principal against three years of coupon.

The line to pull is book value per share, quarter by quarter, going back at least three years. Mortgage REITs report it and it's the honest scoreboard. Economic return is dividends paid plus the change in book value. If book value slid from 14 to 10 while the company paid out 1.30 a year, they were earning the spread and giving back capital at the same time. Also check where the price sits against that book value. A persistent discount usually means the market disagrees with the marks or the leverage, and you want to know which before you decide it's cheap.

Pull the 10-K and read the funding section rather than the earnings release. You want the repo maturity table, the average cost of funds, and how much of the balance sheet rolls inside 90 days. Separately, the tax character of these distributions isn't uniform across ordinary income, capital gain, and return of capital, and business reserve cash held inside an entity adds another wrinkle. That part is a question for your CPA, not a forum.

Two structural facts explain your 12 to 9.

First, a mortgage REIT's earnings come from the spread between its borrowing cost and the yield on the mortgage assets it holds. Most of that borrowing is short term and reprices fast, while the assets are long dated and reprice slowly. When short rates rise or the curve flattens, the spread compresses and the same portfolio produces less income against the same equity base. That shows up in earnings before it shows up in the dividend, and management often holds the dividend for a while, which means part of the payment is being funded out of capital.

Second, the market prices these on book value per share, and book value moves with the mark on the mortgage assets and with any hedges against them. Widening spreads knock down asset marks even when no borrower has missed a payment. A share price that falls while the dividend keeps arriving is usually book value erosion, not a mispricing.

So the yield on a screener is a payout rate, not a return. The measure that matters is economic return, dividends plus the change in book value per share, over several years and across at least one rate cycle.

What the answer depends on for you is holding period and tolerance for principal swings. Reserve cash that might be needed inside two years sits badly in a levered, rate sensitive, exchange traded instrument, because the timing of your withdrawal, not the strategy, decides your outcome. Money with a long horizon can absorb the mark to market and collect the spread. Decide which bucket the 40k is in first, then look at names.