This is usually a version of a "babysitting scam", where some generous out-of-town person wants to pay you a royal ransom for some minor errand or babysitting someone you've never met. It goes a few different ways, but it's usually some version of asking for a quote of what it might cost, and then wanting to pay you in advance. They'll usually want to pay with some sketchy method like needing you to sign up for an account on some website (they'll try to steal personal/identity information or give you a virus to steal more info), or Western Union/Money Gram or PayPal.
They will then inevitably try some variety of overpaying you and asking for some bizarre method of returning them a portion of the over-payment, like "oh just send me a money order/check" or asking you to Western Union the money back to them (especially if they paid you by check or some other such method). The key is the money you return is non-refundable, but the method they paid you with can be stolen accounts/funding, or reclaimed/cancelled (bouncing a check or counterfeit check/money order). You end up with less than nothing, because the income is gone and your "refund" to them is gone too.
Sometimes they'll just ask for your banking information to "deposit the money with you", but they will need illegitimate info to do it like your bank account and login, or information that can be used to steal money from you (bank account and routing information that can be used for payments), etc. Sometimes there'll be some crazy reason.
They'll also often have variants where they are out of the country, have some weird imaginary legal issue they try to rope you into, claim they are in the military for similar reasons, etc. They could also try to deposit fake/stolen funds and then try to rope you into an accompanying scam where they try to shake you down as if you violated the law (they'll pretend to be investigators, police, or organized crime, depending on the situation/scammer).
Sometimes they want money, sometimes they just want to steal your personal information so they can steal from you or sell your identity to someone else.
I've seen the same base scam in business, where they instead want a quote for some large order, often with some urgency and willingness to pay a premium, or for hiring a consultant, etc. All the same base methods, just with a different 'hook' to get you in.
Just replying will only waste your time and ensure you get more emails as you'll likely get added to "known potential sucker" lists. The danger is getting drawn in to the web of lies they use to scam - some of which are stupidly obvious, and some of which are really quite clever and drawn out.