Rather than an EPC of E, from 2030 your investment property will need to be raised to a C. In practice, this means you will need an absolute minimum of wall & roof / loft insulation (to modern standards), double glacing, heating controls, and a boiler that’s less than 10 years old.
You can do better than a C though.
If your tenants have a total income of less than £31k, or if they are in receipt of means-tested benefits (including Universal Credit), or if they have a health condition related to their heart or lungs, that impacts their mobility, or an autoimmune condition, your property might be eligible to get a full suit of eco-retrofit upgrades, enough to take your property to a covetted EPC B.
Apart from meeting your legal obligations early, you’ll have grateful tenants, and improve the value of your home by 10-20% according to recently published studies in the UK. Win-win!