Moving House Uk Mortgage And House Moving Question In The UK?

Mortgage and house moving question in the UK? - moving house uk

What size mortgage can get the annual income of € 65,000 to?
We have a house with a mortgage of £ 70,000, now worth over £ 170,000. I saw a house that you buy at £ 250,000.
because the weather is bad, for sale, I was asked whether it would be possible, in order to rent it, but still had the mortgage for another?
Man thinks he should sell the only option, or we stay where we are, and expand our house.
Suggestions please?