Sumba has a range of guesthouses and hotels in the main towns and a handful of beach resorts so there’s something to suit every budget. The resorts tend to be fully booked most of the year round so you’ll need to book ahead. At the lower end of the budget, you’ll get a good, clean room but expect to pay more for hot water and air-conditioning.
Away from the major centres, accommodation is limited to homestays or with a local host in a private family home. The latter is not hard to find; just ask around. However, remember most families are fairly poor so don’t expect them to feed you unless they offer. Either way, you should bring something to share such as fresh fruit or biscuits which are luxury items to many on Sumba.
On the topic of food, be aware that unlike most of the rest of Indonesia, restaurants, warungs and night food markets are rare on Sumba. This is simply a reflection of the fact that most Sumbarese can’t afford to eat out. Look for warungs on the main street of town and in Waingapu head down to the old harbour where there are some good fish stalls.