About to look for new mortgage..

Hi All

I'm about to look for a new mortgage for a property I'm hoping of buying for £165k. I have a 10% deposit.

I'm also the joint owner of a flat which is rented out to a tenant, and which has a BTL mortgage. My 50% of the rental income is £225, and my 50% of the (interest only) BTL mortgage is £78. Is there anything in particular that I need to do with regards to this BTL mortgage, when looking for a new second property mortgage?

Thanks
SD