Immmediately, if not sooner.

ASAP

It depends.  After business hours - the following business day.

As quickly as possible and at a reasonable time of day even if they are in a different time aone.

Before they can check for messages. AKA 'YESTERDAY'

immediately....

ASAP

ASAP!

Couple hours or so.  Depends on when it arrives too.

The best results will come with immediate responses. 

During business hours, the sooner the better.  After business hours, discretion on the time and subject would be prudent.

Reasonable is in the eye of the beholder.  If you mean the best response time to capture the lead, it seems people want it immediately.

It would depend upon the nature of the lead.  An obviously fake name, a phone number that the web indicates is a spammer type number, a message that does not make sense, among other factors, all help to determine the priority level of responding.

I'm not going to trip over my dogs and spill my beer while sprinting to the laptop to answer, but I'll get back with them as soon as I can.  

As soon as possible.

Anthony,

ASAP

Buyer or seller lead, right away. Rental lead ???? Not so much the same day.

Immediatly.

Anthony Acosta As soon as you open the email.

An immediate response is not usually fast enough.  Many of the leads coming online are coming from the Millennial generation.  This group demands immediate response and send multiple requests.  They also are the slowest to respond and hardest to reach.

As quickly as possible.  You snooze you loose.

The sooner the better.  They can easily email someone quickly if they do not get the information they want.

When I see it.

ASAP and nothing less.

I have automated text that responds immediately and decent response with it

Anthony - As soon as possible, and hopefully within a few minutes.

As soon as possible, or they will move on to the next agent.

Good morning Anthony. I respond as quickly as possible, thank them for their inquiry ask the best way to communicate with them, phone or email. Over 50% respond within one hour. I will follow up with the others the next day, but not many respond after that.

Anthony Acosta - well, they say, respond in less than 5 minutes.

I tried that and the leads went away - they were afraid of me!

When I took time and communicated slowly, I got them on my side.

(And that's just me - not sure how others have felt about it.)

As soon as you possibly can. I answer email and text messages quite fast.

Depend on who its from, it's probably already to late. You should have responded yesterday.  That's why I don't take internet leads.  Either that or when you call, they don't know what you're talking about.

Anthony,
The agents who process thousands of such “leads” say that if you don’t respond it just a couple of minutes the value goes to near zero.

Email leads expect a quick turn around, but if it arrives late at night, first thing in the morning.  

As quickly as possible.  The only problem is that with all of the hundreds of listing spam emails we send each other, it's easy to miss a good one.

Right away

As soon as I can, my clients do not expect me to be hovering over my laptop 24/7 but I am sure the appreciate a response within a day or two.

I would say an hour but most leads don't wait five minutes.

As soon as "practicable", in legalese.