Broken verbal agreements related to rental space between landlord and tenant?

For April and May, I have rented a 20x20 space for $400/month in a very large room (4500 sq ft) to be used as a photo studio. The leaser agreed to let me sublet or rent the large room to other photographers on an hourly or daily basis. The agreement was verbal while awaiting a formal written contract could be created, no problem since the room needed to be finished prior to renting it out anyway. Both parties agreed that the 50/50 split of all monies collected for the rental of the large room would be justified by the leaser contributing the building and all the amenities and I contribute marketing/advertising and bringing the customers in. The room needed paint on the unfinished drywall and the concrete floor needs holes and cracks filled. Leaser keeps backpedaling on their participation, slowly refusing to contribute time or money. One month later, I have paid $600.00 to a painter, 200 in paint and supplies I created the contract but now they don't want to sign. To walk away would be to give them a freshly painted room (4500 sq ft) as well jeopardize my rented space within this large room. Worse than losing the money and time, I really really believed renting this room to other photographers was a goldmine. Proof is, I submitted 3 separate surveys on CraigsList including photos of the room/studio and description of the intent, got over 45 overwhelming YES! responses. I hate to walk away from this unbelievable studio just because a couple of guys can't own up to their promises of finishing the room first or sign in ink what they are so easy to promise in words. Forget the promises of installing WiFi or installing a kitchenette. I can live without that. I just don't have any faith in them anymore and they are really dragging their feet on sighing anything tangible. I have all those responders asking for dates they can come shoot! What do I do?? To start this per diem photography studio where no other exists is a dream. How can I get these two to own up to their promises about splitting the work and costs so we can split the profits??