276 13th Street (5 One 5 Condominiums)

A 5,412-square-foot corner lot, about 18,600 gross square feet built, per PLUTO. The unit plan can be read from the lettering. Floors two through four hold three apartments each. Above the fourth floor the A and B lines drop out and the C and D lines take over, two per floor, up to the seventh. That points to a smaller upper floor plate, which in a contextual district usually means a setback above the street wall. Upper-floor units are therefore fewer and likely larger or better exposed.

In the 2008 sponsor sales, the A line and some of the upper-floor units brought the highest prices. Square footages, bedroom counts and outdoor space are not in the public record we reviewed. Take them from the declaration's floor plans or the unit's listing history.

Fifteen residential owners and one commercial owner. The commercial unit's share of common charges is the main operating question. The declaration will say what share of the building's costs the retail unit carries, what it controls, and what it can be used for. Ask for that page first.

An elevator adds a service contract and, eventually, a modernization cycle to a small budget. At seven stories, the building is also subject to the Local Law 11 façade inspection cycle, which applies to buildings taller than six stories. Ask the managing agent for the current budget, the reserve balance, the elevator contract and age, the most recent façade filing, and any assessment in the past five years.

Ownership form: Condominium, fee simple. No ground lease appears in the recorded documents.

Real estate taxes — 421-a, 25 years. Department of Finance exemption detail shows code 5114 (421-a, 25-year, no cap) on every residential lot, with a 2006 base year and a 2010 benefit start. The exemption covers assessed value above the pre-construction base, not the whole bill. On the standard 25-year schedule, taxable value rises in four steps from 2031/32 and the full bill arrives in 2035/36. Underwrite both numbers on the specific unit.

Everything else must come from the managing agent. We hold no offering plan, by-laws or house rules. Right of first refusal, pets, leasing and minimum lease term, any transfer fee, and the commercial unit's permitted uses are not established here. Also ask counsel whether renting a unit during the 421-a benefit period carries any rent-registration obligation under the program's terms for this building.

Model the abatement to its end. Full exemption through 2030/31, phase-out through 2034/35. Price the unit on both the current and the post-abatement tax bill.

Read the commercial-unit provisions. Its share of common charges and its permitted uses shape both your costs and what sits beneath you.

Upper floors are a different product. Two units per floor from the fifth up. Compare them with each other, not with the three-per-floor lines below.

Lead with the elevator and the abatement. Few South Slope buildings this size have either. Give buyers the tax schedule with dates, not just "421-a."

Explain the two addresses. Buyers and their lenders will find 515 Fifth Avenue on every city record. Say so in the listing.

• 228 13th Street (The Ainsley) — new South Slope condominium a short walk west on the same street; unabated, with deeded parking
• 205 12th Street — six-unit condominium a block north; the boutique comparison
• 445 5th Avenue (The Slope on Fifth) — Fifth Avenue condominium with retail below; the newer counterpart on the same avenue
• 162 16th Street — 2008 South Slope condominium; same vintage, larger scale
• 155 15th Street — 2011 South Slope condominium with garage units
• 372 15th Street — 2005 walk-up condominium nearby; the no-elevator alternative
• 279 Prospect Avenue — 2004 South Slope condominium with parking and storage
• 1638 8th Avenue — Windsor Terrace-edge condominium of 2010–11 with parking