There are plenty of guest housed in the 4,000/= to 30,000/= around town, many clustered near the bus stand. Quality varies but you'll get what you pay for. Tell a taxi / tuktuk bajaji driver how much you want to spend and they'll take you to somewhere appropriate.
Msemo (aka Southern Cross)
Shangani
$50
This is the main only tourist place in town, it's right on the sea front and offers wonderful views over Mikindani bay.