The short answer
Bookkeeping for a property manager is three ledgers that must agree: what each tenant owes and paid, what each owner is owed, and what the business earned in fees. Letting keeps the first two for you and calculates the third. It does not replace QuickBooks, Xero or your accountant. It feeds them clean, per property figures, so the month stops ending in a spreadsheet.
At 20 owners a manual close is easily a full day. The work is repetitive: match deposits to tenants, add repair invoices to the right owner, take the fee, subtract, write the statement. That is exactly the work the software does from the same bank file you already download.