Tenant been in house 10 years but no agreement!??

Hi all,

i am looking to buy a house in auction,the tenant has been in the house 10 years,and it sold in auction in May, with no tenancy, its is now going back in auction. When it sold 1st time round, there was no tenancy, in place, it is now in auction with a 12 month ast signed as of November!!

being as they have been there so long, is there anything to look out for? now a tenancy has been signed is it ok , even tho they have been in there a while.

sorry to drive very one mad but do not want to drop a bollock, also will lenders take a bad view as it tenanted,rather than vacant when going for the mortgage! all mine are with midshires if this matters