Hi Faymoor
From your question it sounds like you currently don't have a mortgage - so borrowing £60,000 against a property value of £135,000 will be relatively straightforward.
Any prospective Lender will want to make sure you can afford the mortgage from your income at the outset- and ideally would be looking for a joint income of over £20,000. They will also assess your past credit history - and the type of property you live in. Your age will be assessed in conjunction with the term you choose for the mortgage, because if the mortgage goes over your retirment age, the Lender will need to know how the mortgage will stil be affordable. It does seem as if you are proposing to sell up at this stage anyway - and your Park home will be ready. Sounds a great plan!
The term of the mortgage and the type of repayment you choose is something that you should discuss with a mortgage expert, they will also help you chose the best mortgage product for you - there are so many available! As ever, the team of mortgage consultants here at moneysupermarket would be pleased to arrange the right mortgage for you when you are ready to proceed (0845 345 5705).
Thanks for the question
Louise