Is your friend an employee of a Non-Profit organization, a School district or is he incorporated as one himself or is he a Minister? A 403(B) plan, also known as a "Tax Sheltered Annuity" is a retirement plan for certain employees of public schools, employees of certain tax-exempt organizations, and certain ministers. In order to use a a 403(B), he would have to qualify as one of those. Even if he did work for such an organization, there is no way he could take the proceeds from a mortgage re-finance and add it to his retirement account.
IRS Publication
571 talks about these types of plans.
Here is an excerpt from Pub. 571 stating who can set one up;
Who Can Set Up a 403(b) Account?
You cannot set up your own 403(b) account. Only employers can set up 403(b) accounts. A self-employed minister cannot set up a 403(b) account for his or her benefit. If you are a self-employed minister, only the organization (denomination) with which you are associated can set up an account for your benefit.
I'll assume you and your friend are aware of the inherent risks involved in using borrowed money to invest with, so I won't belabor that point.
If he is looking for some sort of investment account that would provide Tax Deferral on that large of a sum as an initial deposit, to my knowledge there is none. He could open a Traditional IRA or a Roth but the contribution limitations are such that only $5,000 or $6,000 (depending on his age) could be put into it per year. He could however use a variable annuity product where the gains would be tax deferred but I have a feeling that is not what he or you were hoping for. The IRS is fairly strict on tax deferred accounts and how they are funded.
It is quite possible I am drawing a complete blank on an obvious solution so if I think a better alternative, I'll add to the thread.