A friend of mine does high-end kitchen & bathroom redesigns (she's been on HGTV, etc), and has a commercial space with a showroom that has a fully functional kitchen -- approx 1500 sq ft.

She has offered to rent her space to me, so I can become legal. I know I need to talk to the health department, etc., to find out what I need, but can anyone share some of the things needed to have a legal kitchen.

It's commercially zoned, but is essentially just a regular kitchen. Giant island w/ granite countertops, dishwasher, fridge, stove, ovens and cupboards. Tile floors.

My concern is what it may be missing.

The most time efficient way to get the answer to that question is to call or visit your health department or dept of agriculture (whichever is the regulating agency) and discuss it with them. We might know but they definitely know. Since they have to inspect it why not put the Q&A on them and reference their answers when they do come to visit. Once they tell you what they would like to see then members in forum can tell you how to apply it.

That path worked for me earlier this month when I miraculously passed mine.

You'll be fine.

The biggie for me is triple sinks plus handwashing sink. Does it have that? Yes, best to check with your local Health Dept.

3 compartment sinks w/drain board, hand sink, mop sink, stainless steel work surfaces and non porous walls, floor and ceiling. Proper ventilation via natural or mechanical means. Can be closed off via a door. Commercial grade NSF approved appliances, except the freezer. That's what they required in WI. Hope it gives you a jumping off point. Definitely give the HD and email- they will be able to give you some print material to go off of before you go through the trouble of an inspection. Good Luck!