Here is what convinced me:

Applying these principles, a homeowners association generally does not promote community welfare if all of the association's facilities are closed to the general public (i.e., closed to nonmembers of the association). See Flat Top Lake Association, Inc. v. United States, supra at 111-113. It follows that if a homeowners association has one facility that is closed to the general public, then that facility is not substantially related to the promotion of community welfare. The income from that facility is subject to the unrelated business income tax unless an exception applies.

The IRS does not contend that the Association's tax-exempt status should be revoked. It concedes that most of the Association's facilities and services are open to the general public. Its contention is that income from the portion of its facilities not open to the general public (i.e., the beach club and the parking lots) is subject to the unrelated business income tax because the operation of these facilities is not substantially related to the promotion of community welfare. We agree. The parking lots and the beach club are not accessible to the general public.4 Only Association members and their guests may park in the parking lots. Although the beach club allows both Association members and nonmembers to access its food and beverage services and its restrooms, its primary facilities (the swimming pool, gym lockers, and showers) are accessible only to the Association's members. Thus, the operation of the parking lots and the beach club is not substantially related to the purpose of "[promoting] social welfare" within the meaning of section 501(c)(4) because they are not open to the general public. Thus, unless an exception applies, the income attributable to the operation of the parking lots and the beach club is subject to the unrelated business income tax.

So, since it is apparently ok to not allow the public to use one or more business amenity so long as OPA pays any tax on profits for each separate business, OPA does not have much to worry about except the Beach Club and the marina.

Ramps can be closed to the general public as there is no income and thus no profit. The racquet sports courts, aquatics, golf, YC, etc. can perhaps be closed or not closed to general public so long as they do not produce a taxable profit. There is no indication as to the extent OPA could close non-profit-making entities before the IRS might be concerned.

Still, there is the issue of OPA needing non-members to help support these business amenities. I think an argument can be made that non-members are needed. Regardless of tax issues, there are not enough members supporting many of the business amenities to even make an operational profit, much less a net potentially taxable profit.

Thus, the issue for consideration should not be whether or not business amenities are open to the general public, rather any differential charge to be paid by non-members and still stay within any tax code issues.