[nagrom42]

If you absolutely need to take this offer, draft up a written agreement outlining all the terms you two have verbally agreed to. Have you and the other party sign the form and email yourself and the company a digital copy of the signed form. Also, ask your boss to reply to the email and confirm the agreement to be valid.

[nagrom42]

Given the fact that they were not willing to pay for any legal fee to get you onboard, I would be worried about whether they would actually fulfill their promise of providing you visa/GreenCard sponsorship down the road.