To be honest it's impossible to say based on the information you've provided... What is the lowest price the vendor is willing to sell the property for?
What maybe a good price in one part of the country maybe a terrible price in another. Furthermore, the condition of the building needs to be taken into account. Will you be purchasing the property with full Vacant possession. If you sell a Long Leasehold on the flat then no you wont have the same liabilities as if you let on a shorter lease such as an ast. You will be required to maintain the structure of the building, but you will be entitled to recharge a portion of this back to the long lessee.
You really would be better off taking specific advice from a specialist near to you. They will probably save you the amount of their fees in a reduced price or another area anyway.
The opinions I give are simply my opinions and interpretations of what I have learnt, please do not act upon said opinions without consulting with a suitably qualified professional.