is a 24 unit coop a considered risky for investment

92 1/2 units is perfect

Most basic answer is that it depends largely upon your personal finances. Assuming the coop is financially strong and everything else checks out, how much risk can you assume? If there is a need for major facade work costing $750,000, or a new roof is needed at the same time the elevator breaks, furnace goes and a shareholder goes into default, can you pony up the special assessment that will be levied? In a 140 unit coop, 1/140 of any expense is obviously more bearable. If your finances are such that you can run the risk of a big hit from time to time, then the smaller building may be something you can consider.

Personally, I wouldn't get involved in a building that small because I'd feel compelled to get involved on the board to protect my investment and fret about it all too much. For me, it is a larger building that is appropriate.

I prefer a smaller building, mainly because I don't like living in big buildings. But, I'm more concerned with the actual "living" part of my apt, as opposed to the "investment" aspect. From an investment standpoint, I'd care more about the condition, and less about the amount of units. And, the fewer amenities, the better (less things to have to replace/repair, like an elevator).