What does this rental return?

There is no universal answer — a "good" cap rate is relative to the market and the risk. Stable, high-demand metros tend to trade at lower cap rates, while smaller markets and rougher properties trade higher because buyers demand more return for more risk. The useful comparison is against recent sales of similar properties in the same submarket, not against a national rule of thumb.

No. Cap rate is computed from net operating income, which excludes debt service by definition. That is a feature: it makes the number about the property rather than about your loan terms. To see what the deal returns on your actual cash after the loan payment, use the cash-on-cash section of this calculator.

Property taxes, insurance, maintenance and repairs, property management, owner-paid utilities, HOA dues, and a vacancy allowance if you budget one. Not included: loan principal and interest (that is debt service), and usually large capital expenditures like a roof, which many investors fund from a separate reserve rather than monthly expenses.

Both, for different questions. Cap rate compares properties independent of financing, so it is the right tool for screening listings and comparing markets. Cash-on-cash measures the return on the actual cash you put in, under your actual loan, so it is the right tool for deciding whether this deal beats your alternatives for that money.