If our TN status is expiring, how can we stay in the United States while applying for EB-5?

Just having a pending I-526 does not give you permission to remain in the United States. You must maintain lawful status to adjust when the I-526 is finally approved. Nonimmigrant visas such as TNs and E-2s require you to demonstrate you do not have immigrant intent, but the filing of an I-526 could be construed as evidence you do have immigrant intent. There are other visas such as H1Bs or L1s that do not have this intent issue.

Your situation appears rather complex as it involves switching from a TN to possibly an E2 while an EB-5 is pending. The requirements for E2 and EB5 are remarkably different. Also, pursuing both forms of visas involves a substantial amount of money particularly when filing both E2 and EB5 simultaneously. Advisably, consult an immigration attorney for a selection of the preferred proceeding.

Unfortunately, a pending I-526 petition does not provide an immigration status or work authorization in the United States. To be able to adjust status in the U.S. to conditional green card holders after the approval of I-526 petition, you need to maintain an underlying immigration status. Otherwise, you will need to consular process for immigrant visas abroad after the approval of an I-526 petition. You may apply for an E-2 change of status prior to the expiration of your status inside the U.S. or consular process for E-2 visa in Canada. E-2 visas require nonimmigrant intent, which may be difficult to demonstrate with a pending immigrant petition (I-526). You may consider an L-1A visa if you qualify, which is a dual intent visa and will not require you to prove nonimmigrant intent. You should consult an immigration attorney to review all possible options.

First, it is important you maintain your lawful status in the United States either through another job offer for you or your wife that requires a professional degree and is listed in Annex 16 to the North American Free Trade Agreement (NAFTA) or, as you suggested, by making a qualified, substantial investment with which you can qualify for an E-2 Treaty Investor Visa under the NAFTA Agreement. Alternatively, if there is insufficient time, you could wait in Canada and, once you are scheduled for your final interview at the appropriate American Consulate, you could apply for your immigrant visa and return to the U.S. at that time.

Yes, you can change status to E-2 while your EB-5 is pending, by either using the EB-5 invested funds (if it is a direct investment) or by investing in a different commercial enterprise which you will own/operate or manage.

The problem with changing to another nonimmigrant category visa such as E-2 after filing the I-526 immigration petition is that you have shown your immigrant intent, which is a basis for denial of such nonimmigrant visa. If your I-526 had indicated you will seek to pursue immigrant visa applications through consulate processing, then your lawyer may be able to argue E-2 will not lead to an adjustment, as you intend to interview in Canada for the immigrant visa.

The best option is to get an extension of the contractor, if possible, to get a new job in a similar position. However, if there is no viable TN option, the E-2 investor visa is absolutely an option you will want to investigate. You can either apply to change status to E-2 or apply for an E-2 in Canada at the consulate. This latter process may take at least 2-3 months to process.

You should speak with an experienced immigration attorney to determine whether you might become eligible for a change of status to E-2 or an actual E-2 visa application at the appropriate U.S. consular office in Canada. If you make a qualifying investment in a U.S. commercial enterprise and you can develop and direct the operations of the entity, you may be able to qualify for E-2 (and your family would receive E-2 dependent status).