Renting room in our house to lower 18600 threshold

hi guys thanks in advance for any help you can give us.
Our intention is to get a lodger in our 3 bedroom house who will sign a 1 year rental agreement between this April to April next year. He will pay rent of a total of £600 per month.(We own house in full)

We intend to submit the following evidence:
EVIDENCE 1 - a letter from the “estate agent” to say the house is big enough for multiple occupants and that it is a 3 bed house etc.
EVIDENCE 2 - My bank statements will show the income for the last 6 months between April and October and will back up the rental payments being paid into my current account
EVIDENCE 3 – Rental agreement document between me and tenant

This is acceptable as a plan?

Can we use this with cash savings?

How much will this bring the cash threshold down by? We worked out 4600 is that right?