From Boats-US:
Resale value, w/ 2000 motor, is estimated to be in the $18,000 - $22,000
range, although, noting the age, the specific vessel could just as
easily be properly priced somewhat higher (or significantly lower).

We would, however, given the at least semi-custom nature of houseboats
in general and the many intensely localized value centers, strongly
encourage an informal, "sense of things" surveyor consultation prior to
making any marketing decisions.

The value estimate above is based on research and the experience of
BoatU.S. staff. We recognize that the range of values for houseboats can
be huge, depending on condition, equipment, the degree of customization,
local preferences, etc. BoatU.S. recommends that you make arrangements
for a marine surveyor to provide a report on the condition and value of
the specific vessel within the overall context of the local market prior
to marketing it for sale. See http://www.boatus.com/insurance/survey.htm
for a marine surveyor referral list. This is a list of marine surveyors
approved by BoatU.S., and they're posted geographically.

Regards,

Sandy