Finding a lodging place in Hanoi depends mainly on your budget. You can rent a room in Old street quarter starting at about $15/night. There are also fully luxury ones that can be upwards of $500, and everything in between. Preferable areas for tourists are in the central area (in the Hoan Kiem or Ba Dinh districts) or in the Tay Ho (West Lake) suburb (about 15 min. from the central area).
... Everything went perfectly and we had a great stay. We were very happy with your service, and will certainly recommend you to our friends. And we hope to go back and stay at Domaine de Tam Hai next year ...