Membership in boatominium an asset?

I have owned a "membership" in an incorporated association known as a boatominum. It gives me the right to use one particular wet boat slip. I have used this for my own vessel for years, however, during the past several years I have rented the slip, declared the income and the expenses (dues, assessments, dredging costs, etc). I now have sold the membership. My question is whether the "membership" is an "asset" and if so, is the difference between the original cost and the sales price considered a "capital gain". Associated with this, should it be considered an asset, what type of costs over the years that were paid separately (such as dredging assessments) or various costs that form the budget for the boatominium, which are split up and charged to members as "monthly dues"are considered costs to be added to the "basis" (my original cost of the membership?

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