I gave them a video tour. 

I will give you a quick tour of the area or meet you for coffee 

The city is still one of the most beautiful in the USA and the only one with significant European style walkability and architectural and natural charm.

In reference to Ned's advice of finding comparable values, use recent comparable sales prices (zillow) to estimate current value--be cautious of props that sold recently needing repairs/rehabs.When talking with sellers--before making offers/discussing money, find out their motivation for selling & try to build a rapport (commonalities you have) as you tour through their property and find what their REAL needs are respect to the price (ie. bal. on mortgage, if $$ is needed for down payment on next prop, selling to settle divorce, selling as they inherited prop they didn't want, moving out of town, etc.), and whatever dollar amount the seller mentions, you restate it as a range working in your favor.

Totally by accident, I also started a tour company in Panama to assist people who are considering relocating here.

They've seen pictures of the house but no tour of the house.

@David Zheng,That's rough, I hate when something small an unintentional jumps up and we end up on the apology tour.

I toured the house and took pictures with the homeowner.

I'm a 5 minute drive from the property, I know the area, I personally screen them and tour them, it works for me.  

I inspect all houses but honestly you don't need a seller to give you a tour.