The small end is real. It's just tighter than the listing email suggests.
Take your pad. Land $410k. A 2,500 foot single-tenant shell at, say, $300 a foot is around $750k of hard cost, and site work on a pad often adds $150k to $250k because you're paying for the drive aisle, utilities, and drainage even on a small building. Soft costs (design, survey, geotech, permits, legal, loan fees) usually land somewhere around 15 to 25 percent of hard cost. So you're modeling a $1.5M to $2M project, not a $50M one.
Construction lenders size to cost rather than to a purchase price, and 60 to 65 percent loan to cost is a common bank range for a small commercial build. That leaves $600k to $800k of equity. Get the actual sizing, rate, and reserve requirements in writing from a lender before you build any model, because those terms move around.
There are two smaller doors. You can invest as a limited partner in a development fund or a single-asset deal, where minimum checks often start near $50k to $100k, and you have no control. Or you contribute land into a joint venture and let a sponsor develop it.
One thing the equity number hides. On a deal that size the bank will almost certainly want a personal guarantee plus a completion guarantee, meaning you personally finish the building out of pocket if costs run past the budget. That guarantee is the real gate at the small end. Plenty of people have the $700k and still can't get the loan, because there's no balance sheet standing behind the promise to finish.