In practice this means two separate affordability calculations running simultaneously. We coordinate both to ensure the right lender is used for each property, that the applications are submitted in the right order, and that neither transaction puts the other at risk.
Let to buy works particularly well for homeowners who have built up good equity in their current home, whose property is in a strong rental market, and who are ready to move into something larger or in a different area. It also appeals to those who do not want to sell in a slow market, preferring to hold the property until conditions improve.
Before deciding on let to buy, it is worth modelling out the full financial picture. This includes what your new residential mortgage will cost, what your buy-to-let mortgage will cost, what rent the existing property is likely to achieve, and what your net position looks like after tax. Section 24 changes mean rental income is taxed differently for higher rate taxpayers than it used to be, which affects the calculation.