My son runs his own business and they would not give him a mortgage till he had produced 3 years of accounts.
You say you want to start your own business but many many businesses fail so how do you know even if you did start your own business you would be able to keep up the mortgage payments.
Whats wrong with ploughing all your money in the property, money earns little interest in the bank at the moment.
And if you buy the house outright you can then concentrate on running the business without worrying about earning enough to pay the mortgage.