Overseas Mortgage lenders usually base their lending decisions upon what they call a debt to income ratio. They allow a certain percentage of your disposable income and this must cover any debt payments you make including mortgage payments, credit cards or loans.
All income must be provable either by way of pay slips if you are employed or accounts if you are self-employed.
Like UK lenders, overseas lenders will have a maximum percentage that they will lend against a property value, this varies from lender to lender and country to country.
You will need a solicitor to carry out conveyancing on your behalf, it is extremely important to use a solicitor who is familiar with the country you are buying in and is independent.
It is important to get professional advice when borrowing overseas, to ensure you get the right product for your circumstances.