First off any airplane is NOT inexpensive. ALL twins wil run about 3x the maintenance and hourly costs as a single.
An Apache or Twin Commanche (both use 160 Lycoming 0-320s .. well later model apaches do anyway as do all the Twin Commanches). This equates to a low fuel burn .. 16.5 GPH (total) in cruise.
You can find a decent Apache for about $50k (probably about $80-100k for the Commanche). The only thing you have to watch out for on the Apache is parts are getting hard to find. Hard to find parts = expensive parts/work-arounds.
As far as the wisdom goes towards building time. I think it's a good idea but it's really up to each person and more importantly, their budget.
I was a part owner in a Twin Comanche for a few years.
We figured our total cost, fixed and operating, at about $120 per hour (based on 150 - 200 hours a year).
I flight planned 155 knots and 15 gph @ 65% power.