The old couple immigrated to Canada.

In Canada, a guarantor usually needs to meet certain requirements to become a guarantor. These requirements include:

1. The guarantor must be a Canadian citizen or permanent resident and meet certain residence requirements.

2. The guarantor must be able to provide enough economic proof to prove that he can afford the guarantor's living expenses.

The guarantor must pass the background check to ensure that there is no criminal record or other circumstances that do not meet the guarantee conditions.

If the guarantor no longer meets the above requirements, or other irregularities occur during the guarantee period, the guarantor may be revoked. For example, the guarantor may be revoked if he loses his Canadian citizenship or permanent resident status, or if his economic situation changes significantly.

In addition, if the guarantor himself does not meet the immigration requirements, or violates the immigration regulations during the immigration period, it may also affect the guarantor's guarantee qualification. Therefore, in any case, the guarantor needs to abide by the relevant regulations to ensure that the guarantor meets the immigration requirements.