Releasing Equity for BTL investment



New Member
My girlfriend and I own our main property valued at £320k with a mortgage of £98k so £222k equity. I have a BTL flat worth approx £100k on a BTL mortgage. We’re both 53, I have very good credit and my partner has poor credit.
We’d ultimately like to release some equity (approx £100k) in order to purchase 3-4 more BTL properties in Cardiff, using approx £25k deposit on each property and taking out interest only mortgages for each property.
Can we use the equity in our house to use as deposits in BTL property? Or is this only through equity release plan at 55?
If not would the only other way be to sell and downsize and use the £100k?