Take the advice of one of the top pressure washer manufacturers and buy the best you can afford.
The more advanced models generally have more power, better accessories, more flexibility and better features like variable pressure that can be very useful.
If you need to buy a basic model, try to buy from an experienced and respected manufacturer.
The brands we stock include names like Stihl and Karcher, well known and respected manufacturers of durable and efficient machines. You can see the full rang here - pressure washers