Accrued interest does not make you poorer. The money returns to your own CPF account. What it changes is the split between CPF and cash, and several costs of the next purchase have to be paid in cash.
A bank loan needs part of the price paid in cash: at least 5% at MAS's 75% limit, and at least 25% at its 45% limit. Check that your cash proceeds cover the cash part of the next purchase.
If you are choosing between selling first and buying first, see the guide to the three routes.
