Every conversion article is a 20 story office tower. Mine is a bowling alley.

Harder per unit, easier to survive. A zoning attorney, an architect, and a survey cost roughly the same whether you're doing 6 units or 60, so those soft costs land brutally on a small deal. The upside is you can actually finish it.

Single story clear span is the friendliest thing on your list. No floor plate depth problem because you can cut skylights and courtyards in a roof, and no stacking constraint on plumbing since everything goes in the slab or a trench. The catch is you're trenching a slab, which is dusty, slow, and full of surprises.

The bowling alley probably has a lane area with almost no windows in the middle. How do you get light into the center of a 14,000 sf box without turning a third of it into a courtyard you can't rent?

@kestrel that's exactly the trade. You cut a court, you lose maybe 15 to 20% of the footprint, and every unit gets a legal window. It's still often better than the alternative, which is units that fail the light and ventilation requirement and can't be permitted at all.

The bank is the one I'd look at hardest and it's not the vault. Drive through means a curb cut and a site designed for cars, so your parking requirement conversation with the city might be the easiest on your whole list. Parking minimums have killed more small conversions near me than construction cost has.

What's the actual problem with the vault? Genuinely asking, I assumed you just leave it and call it a wine room.

@rigging the problem is demolition cost if it's in the way. Reinforced concrete walls two feet thick don't come out with a sawzall. If it's not in the way it's a great storage room and a fun listing photo.

The church is the trap on that list. Beautiful, and the roof structure, the single volume interior, and the stained glass all fight you. Also churches often sit in residential districts where the zoning contemplates a church and nothing else, so you may be asking for a rezoning in a neighborhood full of people who went to that church. Scope creep on a church is a genre of its own.

Run the arithmetic on the medical office before you fall in love with the bowling alley. 9,000 sf at 70% efficiency is 6,300 rentable, so maybe eight small units. Existing plumbing density in a medical building is already high, exam room sinks everywhere, and that saves real money. It's the least romantic building on your list and probably the best candidate.

@ledger is right about the medical office and I'd add HVAC. Medical buildings often have distributed units and decent shaft space already, which is half the fight. The bowling alley likely has two big rooftop units sized for one open room and nothing else.

The thing that got me at this scale was that lenders don't want to be there. A $1.2m total project cost is too small for construction lenders who want $10m and up, and too weird for residential lenders because there's no house yet. You end up with a local bank relationship or private money at rates that eat your margin.

Also two of your six candidates are probably not for sale, and the church almost certainly involves a diocese or a denominational property committee that moves at its own pace. I've watched people spend a year on a building nobody was selling.

Reading this list of replies as someone starting from zero, my takeaway is that the strategy isn't the hard part, the sourcing is. Six buildings, and the good one is the boring medical office nobody would write an article about.