Unless you need to be incorporated to complete trial sales, market fit testing...don't do it. Wait until you can afford the couple thousand dollars it will cost you and or until you get an investor if you will go for one.

a C corporation is most likely your best bet.

Fairly is all on perspective. The original ideator shouldn't leverage that fact to get more. Equity should be based on time involved, possibility of the individual leaving, value added in the long term picture... once you get employees how critical will this position be? how critical is that value now? Whatever way you split, leave about 10-30% open for future partners or investors or negotiations of any kind.