Do you have to wait till closing to find out about back taxes or liens on a foreclosure property?

Most of that information is available online through the county assessor's office.

Any title company that's been in business since yesterday can run a preliminary title report and tell you that information instantly.

The only thing you wouldn't know is whether or not those liens would be cleared at closing. They usually will be, but if its a short sale there might not be enough funding to pay off all debts against the property in which case you'd be hoping for a bank to forgive the previous owner's debt to clear a lien.

Your realtor should be explaining this to you in more detail if you're trying to buy a foreclosure. If they aren't knowledgeable or aren't being helpful then consider using a different agent.

You can go online in many towns and find out that information. My friend is always snooping to see who owes what.

In general, that's true. Many of these fees are pro-rated based on the date in the month when closing actually happened. Your realtor should be able to give you a pretty good estimate, but it's usually a range because the actual date when a property closes is controlled by many unpredictable factors.

Your agent is wrong or you mis-understood her. That's the purpose of a title search BEFORE closing. The seller is responsible for all back taxes and most other liens.

Your lawyer will check that. They purchase title insurance on behalf of you.