How do I know if legitimate holiday ay let

worrieroffam

I have found a holiday let in North Wales via a post in an accommodation finder in Facebook. There is a Facebook page but with only a very small number of posts. There is no associated website, when I queried this the owner said it’s a work in progress as this is a new letting/business. Only 4 posts in their related Instagram page. They had availability at fairly short notice. Payment is either small deposit £100 and cash on arrival or deposit and bank xfr 3 weeks before. No PayPal option. Only 3 reviews on Facebook?

How do I know if this is a legitimate holiday let? 

Most of the booking competed via Facebook messsnger with exception of a personal email containing link to deposit invoice request (also attached as a pdf)