Lack of Credit History
The main issue that lenders have to consider when deciding on lending to a first time buyer is that you have no track record of paying a mortgage.
If the applicant already has a mortgage then the lender can look at the credit file or mortgage statement to see if they have managed to keep up their monthly payments (they take this as avidence of the likelyhood that future payments will be made on time).
If you have never had a mortgage then they cannot do this and have to make more of a 'guess' at how you might perform.
In this case, it is very important to have other lines of credit, such as credit cards or loans. The lender can then look at your payment history on these credit cards or loans as evidence that you will make your mortgage payments on time.
If you do not have (and have not had over the last 12 months) any credit cards or loans then the maximum loan to value you are able to get is likely to be reduced.
Low or No Deposit
Often much of the deposit for a house purchase comes from the equity released from the sale of the current house. First time buyers can't usually do this and so the deposit has to be saved up (unless a relative can gift some money!).
This can mean that there is little or no deposit.
You can still get a mortgage with little or no deposit, with a High Loan to Value (LTV) mortgage but this does mean that the cost will be a bit higher. The important steps are:
100% LTV. A few lenders will lend 100% of the property value and interest rates and initial fees can be a little lower.
95% LTV. Most lenders will lend up to 95% of the property value but there will either be a higher lending charge or interest rates will be a little higher.
90% LTV. If you can get a 10% deposit then you should be able to access most of the lower cost mortgage deals any lender provides.
This of course depends on there not being any other factors that may effect your eligibility for a mortgage.
In the last month or so many lenders have changed their view on high loan to value loans. Many have withdrawn their 100% mortgages and the ones that are left are being more careful when they lend.
High Income Multiple
Many first time buyers find that they are stretching to the upper limits, the amount of money they need to borrow to buy the property they want.