Staircasing mortgage on a shared ownership property - deposit required?

If you own 25% and will be buying the other 75%, it will no longer be shared ownership. That said, most lenders will not loan more than 80 to 90% of the value of the property. Depending on the size of the mortgage on your current share, you may need more down to meet that requirement. This IS NOT a deposit. It is a nonrefundable PAYMENT toward the price of the property.