Need advice in a situation.

Hello, Hopefully this is the correct category to post this. Since it relates to money/business, I decided to put it here.

Anyways,

A friend who works for a construction management firm in New York called and told me that his company is looking for a specific software, but the big companies who provide these software and hardware are charging them at least 10K to 15K per location (they have 15-20 locations). He explained what the company needed and asked me if its something I could do for cheap 1k for example. Since, my field in real life is not to develop things but I have being involved in the development of software I have some experience.

I took the challenge and in 2 weeks I created what he needed the software and the hardware. The plan was to sell it to his company and other companies alike.

apparently in the construction business, the bank pays for everything. But they only pay after 45 days after reviewing the site (Bank sends a agent every 45 to review the construction). So, if the construction is not going as planned the bank doesn't provide the full amount and the management firm has to put the rest out of pocket. If the constructions goes as planned the bank provides the money for those 45 days. They repeat this cycle until the building is complete.

So, the company wants 15-20 units which is about 15k of expenses in hardware. But, they will pay after 45 days. My friend and I don't have that money at the moment to provide the 15 units. Also, if for some reason the companies decides to cancel everything after all the units are bought, we will lose that money.

Co-worker of my friend (who I dont know, just met him once to discuss the business) says that he will put all 15k, as well as future marketing expenses and contracts ( he saw a value on the software) and has the money.

Here's where I need the advice. I took my friend's Idea and I design the device. I coded the software. I came up with the hardware setup as well as coded the communication between a bunch of things. It took me two weeks to complete and way more than 100 hours. I spent weekends from 7am to 4am the next day doing this thing.

The person who will put all the money gave me the following choices.

1. He will pay me 5K for the 'Initial Software Design'
2. He will will give me 33% after the business is launch. shared between him and my friend, ONLY if I can complete the software by myself.
3. If we required someone to help us (other programmers) to finish the product, he will only give me 10% after launch.

He also came up with features that the thing needs to make it production and mark it as a 'launch product'. So, I know for sure that the features he asked, I can't do by myself. Too advance and definitely requires a team, so automatically I know that I will land on the 10% instead of 33% of the company.

Here is why i'm worried.

1. Like I said at the beginning im not a programmer. So, I know at some point we will need professionals. What will stop him from replacing me and hiring someone after the company has some revenue.
2. I feel like I did all the ground and dirty work, I will also support and continue to code until we get clients (which he says he can provide, since he knows the business and people for 10 years). Since, he will invest and will take all the risk with his investment and 'do the marketing'. He feels that he is entitled of being the CEO of it.
3. I feel like at some point I will be pushed out of something I helped created. Those 10% he promised will become 0% at some point.
4. After he propose to give me 5k for the initial design of the software. I feel like a employee instead of a co-founder.

So, here's where I need the advice? Will you guys take the 10% and the 5k?
What kind of deal would you guys make with them? That way it's a partnership instead of having him be the CEO because he provided the money. Even if I dont have the skills to finish the final product, what kind of deal will ya make to be the CTO, Partners, and Co-founder.

English is not my first language. Help is appreciate.

In my line of work, I would never do anything upfront with payment at a later day, especially not 45 days later and with a risk of non-payment. If I were you I wouldn't go through with the deal at all without upfront payment or some portion of it upfront. Or, if you really want to proceed like you said above, then maybe charge more than just the 15k. At the end of the day, they are spending 10x more already, so even you charging 3k per location would still be cheaper for them and make the risk worth your while if it works out.

It all comes down to how much you trust the situation though as you know it better than any of us here, so you just have to go off what you think is best.