Anyone know end figure guestimates for property?

[twoblacklines]

Say I buy a house for £80k

And estimate letting rate is £500/month.

Which is a 7.0% yield.

What are the end figures ie what goes into my business bank account from this after agency fees etc?

Something like this looks attractive sub £100k http://www.rightmove.co.uk/property-for-sale/prope...

I rent so technically no second home BTL tax??? On the first anyway.

Would be buying in cash with view to leverage by mortgaging it to build a portfolio if there is actually any money to be made through BTL anymore in non-London areas?

Is there any insurance in case the people who rent it, smash it to bits or set it on fire etc when they move out or one of the other horror stories...is this the letting agents responsibility as they found the clients? Or should I skip an agency completely?

Thanks