This is by far and away the best homestay in Hoi An, not only in terms of cleanliness, size, and affordability, but especially in terms of location.
Hoi An is completely overrun with tourists and the little island on which this homestay stands is as close to untouched rural Vietnam that you'll get anywhere near the banana shirts and Korean buses that now comprise the Hoi An experience.
Surrounded by rice fields, short bicycle ride will take you to coconut mangroves, picturesque corn fields, a whale temple inside a boat, and more.
It has a rooftop terrace overlooking palm trees and rice fields and it also has an upstairs kitchen.
The family whose homestay it is are delightful, helpful, accommodating—and Dung (the wife) speaks very good English AND works at Hoi An's best tailor shop and so can get you a great price on your custom-made clothing.
Take it from someone who has spent time in Hoi An for five consecutive years:
Book this homestay.
It alone will make your stay in Hoi An.