You will need either a 20% or 25% deposit depending on availability and your choice of buy to let mortgage products.
The average purchase price of a property is £68K-£80K which means the deposit required is in the range £14K-£20K.
However, because you buy the property at a 20% discount to market value, it may be possible to remortgage the property after 6 months at the full market value.
This would allow you to release the 20% deposit you initially invested and re-invest this deposit in another property. Our broker can organise this for you.