Renters at Island House and Westview face a critical decision over the next several months: To fight takeover of the buildings by the Sheldrake Organization, or to seek something better through negotiation as that process goes forward.

At both buildings, on dual tracks, committees are preparing for both possibilities. At both buildings, one goal has been adopted - resident ownership rather than commercial privatization as rental buildings. The concern is that privatization - removal from the Mitchell-Lama program - could lead to intolerable rent increases. That's balanced, to some extent, by the certainty that a tenant-sponsored buy-out, in itself, is likely to lead to increased housing expense.

At Island House this month, fund-raising has begun with a flier asking $50 per apartment - that would produce a $20,000 fund - to bring a law firm into the process to guide residents through what has proved to be, in other Mitchell-Lama restructurings in New York City, a complex process.

On Roosevelt Island, there are two additional complicating factors: The Roosevelt Island Operating Corporation (RIOC) will be setting ground-rent rates in any privatization, and for all the Island's Mitchell-Lama buildings, tax abatements are about to end. The uncertain cost of each of those "wild cards" makes financial projections difficult. And there's another factor that will affect any tenant buy-out plan: Just how much profit will satisfy the owners?

Negotiations at Westview have already produced a working number: $380 per square foot. It's considered too high, but it serves as a starting point for some calculations.

Without considering the wild-card tax and ground-rent matters, such a number, even if cut by nearly a third, could lead to a purchase price in the $75 million to $100 million range, presuming a willingness by Sheldrake to take a quick profit and avoid years of legal warfare with potentially troublesome residents. But even in that range, the result could be mortgage maintenance and mortgage costs representing an increase in housing cost of $100 to $200 per room per month. (A three-bedroom apartment is considered a six-room unit for such calculations; a one-bedroom apartment is calculated at 3.5 rooms.) Thus, at current mortgage rates, after a down-payment and in addition to a personal mortgage, a two-bedroom apartment (calculated as 4.5 rooms) could face an additional monthly cost of $450 to $900. Before residents would be asked to make a decision on a buy-out deal, the cost of ground rent and increased taxes would have to be worked out and factored in.

These numbers suggest that housing-cost increases are in the future for residents of both Island House and Westview - even without considering any increase in taxes, and any increase in ground rent. In each case, that would be in addition to down-payment costs and any personal held mortgage on individual apartments.

Progress toward a Sheldrake purchase, now considered a firmly contracted precursor to any tenant-sponsored buy-out, is likely to take time. Tenant committees appear ready to resist any change of ownership unless clear terms for tenant-sponsored buy-outs are firmly understood before the State Division of Housing and Community Renewal (DHCR) approves a transaction.

The RIOC Board of Directors pledged, in agreeing to work with the owners of the two buildings on the ground-rent question, to attempt to find ways to protect residents unable to meet increased costs. The numbers generated in buy-out calculations suggest that, even without considering ground rent and taxes, that will be a considerable challenge.