Nothing, you can keep contributing and deducting contributions until you reach the lifetime maximum. The FHSA is so poorly implemented that there are only limitations to opening the account, but nothing forces you to close immediately after purchasing a property.
If you withdraw any remaining property as a taxable withdrawal, you must include this amount as income on your income tax and benefit return for the year the amounts are received. Your FHSA issuer will give you a T4FHSA slip, First Home Savings Account Statement showing the amount of the taxable withdrawal in box 22.
There is no similar rule for FHSA contributions (like there is for RRSP contributions) where in order for FHSA contributions to be deductible, they must remain in the FHSA for at least 90 days before you can withdraw them for a qualifying withdrawal.
I opened an FHSA, but no longer want to use it on my first property. What are my options? You can transfer your funds to an RRSP or RRIF without affecting your contribution room. If you decide to withdraw your funds, the market value of your FHSA will be added to your income at the time of withdrawal.
Wealthsimple FHSA withdrawal should take maximum 4-6 business days but likely less. RBC will be similar. If you're pulling from a RRSP under the home buyers plan it can take 7 business days so that's a little bit tighter.
You must not have acquired the qualifying home more than 30 days before making the withdrawal. you must be a resident of Canada from the time that you make your first qualifying withdrawal from one of your FHSAs until the earlier of the acquisition of the qualifying home, or the date of your death.