pre-funding start-up in tech.
founder had idea and filed patent (pending); developed concept, small cash funding, etc.
engineer came in year later to help shape app; code proof of concept, help with product schema, etc.
now incorporating - what is equitable share & how to structure equity share (stock grant, options, both, etc.) for engineer?
both have full time jobs in other businesses.
Did the engineer just do the work and trusted that you could come to an agreement later? If not, that means you promised something and you have to stick with it.
Otherwise, you should come up with a number of options you can present to the engineer such as:
Your idea, no matter how brilliant, wasn't worth anything until the engineer implemented it. Even now, your patent isn't worth anything if you can't afford to enforce it. Your engineer may well run off and make a business out of his hard work. So you could either do the right thing by the engineer and enter into a proper partnership or, if that doesn't suit him, ensure he is eventually compensated at market rates. Until either of these happens, your engineer may well have you by the balls.