mortgage interest deduction grandfathering

[David Cornett]

Hello,

I bought a property in 2017, which is 'grandfathered' in to the limit on interest deduction.  If I buy an investment property this year, how does the limit actually work.  For example, if I have $500K in debt from purchases prior to 2018, can I only add a further $250K in 2019 without hitting the limit?  Or are basically all of my real estate purchases grandfathered in to the $1M debt limit?

Thanks!