Leting owned property - income tax question?

[Fitiong]

Hi! I'm looking to move to another area of the UK for work purposes, but I already own a property so will be renting there and letting my current property (as much of a pain this is, the job has much better pay and commuting will cost just as much as the salary bonus is!). I was wondering how the money I get from this will affect my income tax? The money is going from letting my current property straight into the rent for the other one, so will I pay income tax on it even though it's basically immediately spent? Looking at this tax tool I will be paying quite a lot of income tax. I'm not quite sure how it works so was hoping someone here does/has done something similar and can let me know how things went with them, or someone who knows what to do can help me out. Any advice will be greatly appreciated!

If I've missed any info out please let me know

Thanks