Is this Mortgage Fraud - yes or no.

[Jeremy Houser]

So I currently own 1 rental property and my fiance and I are looking at this Quadplex.  The seller agreed to a $75k selling price which is a really good deal.  I use to live in one unit out when I was a traveling therapist. Unfortunately, the owner has pancreatic cancer and needs to sell ASAP.   So I contacted my loan originator, and my fiance' was approved for a primary residence loan.  She will also receive a first-time homebuyer downpayment assistance grant.  In order to qualify for downpayment assistance, she has live in one unit for two years. So we can essentially buy the property with 0 money down.  We are going to Paris for our Wedding during Thanksgiving which will be a symbolic wedding and we technically don't have to get our marriage license in the states until after we close on the house.  

If she buys the quadplex and change her mailing address to the unit we will renovate is this considered fraud?  I just want to make sure we don't put her in legal trouble. At our current location, all the bills are in my name. However, it would benefit me significantly if we get married prior to the end of the year for tax purposes.  She has a green card and has to wait until 3 years before she can apply for citizenship.  Ironically, owning a home looks good on your citizenship application.  Is it illegal to buy a house as a primary residence and then get married and live with the husband.  We do have a joint banking account with the same bank that will issue to loan.  

Help me, family.