Going to use approx. figures here for illustrative purposes, though these should be a good indication. Assuming a fairly straight forward tax situation for a single person, a gross income of 55k should mean a net monthly income of around 3,100. Any other debts?
Based on the level of mortgage monthly payments would be around 725-800 on a 150k mortgage over 30 years at 4%/5% interest rate respectively. That's a very manageable per cent of current net income (c25%).
On a purely financial basis I can't see a huge difficulty in being able to sell the existing and buy the new one and being able to fund the mortgage.
The extra ten grand of a mortgage over the existing one wouldn't cost that much extra assuming that the go forward interest rate is broadly similar. Bit trickier if he has a tracker as he would really need that to move or the repayments would be quite a bit higher.
A potential alternative of renting the existing house and renting in the new town where he works is also going to cost. The rent on the existing house will be taxable, net of allowable expenses, meaning in practice some level of tax payment if likely. So this should be factored into the equation.
Brendan is right in indicating that if there are no savings that is a problem as a Bank will look closely at spending and saving. Also needs a deposit.
In theory sounds do'able if it is the right move and the location he wants to live in for a sustained period and with better management and control of finances it should be affordable.
In practice more difficult given current situation, flux in the banks, etc. I recommend he gets all his facts and figures together (income, details of all expenditures monthly), makes an effort to save over the next 3-6 months to show a savings capacity (unless significant expenses I can't see why he can't save a bit, not judging though!).
As usual non financial matters are very important, what stage of life is he at, married/partner/kids (??), location, job stability, etc. Take a read of this also, may give some ideas and food for thought.
http://www.askaboutmoney.com/showthread.php?p=1318784#post1318784