Everyone wants to know how much they should expect to spend, how many members they can get, what to do for traffic, etc. The answers are as varied as the niches we work with, but I am going to try to explain this as simply as I can in a way that will cover the most varied situations. Here goes…
Type of Traffic to Pursue
1) Direct traffic purchase - the fastest way to get members is to buy traffic directly to the site. The problem here is that you have to sift through scammer traffic and even when you get it down to honest sources you can still only expect about 1 or 2 in ten of them to convert well enough with your site to be profitable. So trying to grow your site via this method generally requires a lot of funds because you lose money on 8 or 9, keep one. Next month you buy 10 more and lose money on 8 or 9, keep one... etc. You end up after months with a good bunch of traffic and not having to throw money away anymore, but it cost a lot to get there.
2) TGP/MGP spamming - you can submit your site to the gamut of TGPs and/or MGPs and get lots of free traffic, which helps. The downside (especially with MGP) is it uses a lot of bandwidth, and it usually converts very poorly. You also need a different type of tour to work best with this kind of traffic so if you are doing other means of traffic generating listed here you probably need more than one tour. It's a time consuming venture, but again, it's free traffic so many people go this way to start.
3) Affiliates - in the long run this will be your biggest gain because you are making your dollars work for you rather than work for your dollars. It takes a good few hundred affiliates before you see any real tangible results, and it takes a good six months to a year to get plenty of people. You have to have sites they are willing to try, and you have to have a webmaster program site they will be impressed enough with (including enough ad materials, etc.). All this ads up and can be costly, but, done right, it will be your primary means of growth in the long run. [A self-spamming note here: if you are interested in a conversation about whether to run pay per sign or referral % or per click, see my e-book at http://www.lumyr.com/ebook]
4) Feeder sites - you can get traffic by sending it from sites you already own or build. Have your own TGP or some free sites. A link list. Whatever it takes. There are many people that build their own "free" sites first and then get enough traffic to feed their own paysite and thus do well with little money. It's these people that often have newbies mistakenly thinking they can get rich on a paysite with little money and little time. Someone with a big "feeder" site going into a paysite project to start will make money on day one. If you are starting a paysite first then you have to slog through steps 1 - 3 instead. You can always build feeder sites, of course... but that's more time and expense, so just make sure you realize that.
5) Networking - last but not least is how you can get free traffic via good old fashion horse trading. Do you have content you shoot? Can you program? Do you do design? Trade some work with people for some traffic. Or trade exits. Or whatever you can do. Make as many friends as you can. Be a board whore. Whatever it is. The better you are at making friends online, the quicker you will grow your site on trades. This is another area in which people get mislead into thinking this is a get rich quick biz. Because some people are just astounding at networking and others just don't have the knack. The former can grow fast, the latter may never get there. You're always just a few deals away from the bling.
So the next question I get is, "how many sign ups per day can I expect?" That's just too variable a question to answer properly. If you have $50,000 per month to burn and are great at networking you can set a goal of 50 per day and it's reasonable. If you have no budget and have to rely on time spent doing TGP submissions, you might only get 2 per day. So why do I even bring this up? To make this point; and it's a big one:
Look at the steps above and decide which ones you are equipped to pursue. Then set goals for yourself on how much time to spend on them or how much money to spend and stick to those goals. Be diligent! Don't say you want 10 sign ups per day then wonder why you don't have them if you only spent 3 hours all week networking or working on submissions. Your effort will equal your return. Sometimes you find your efforts in one area aren't working well (let's say TGP submissions are not working out). So you have to adjust.
There's more than one way to get there. If the submissions aren't working either think up a TGP type tour or choose from the other options above to focus your time on. "Real world" companies go through millions in ads and commercials not knowing what the results will be right off. You try and measure the results, then you keep what worked and rework what didn't.
All that said, the original question was "How Fast Can You Grow An Adult Pay Site?" My answer is that it varies according to how much time and money you have, but in almost all instances where you don't own a big feeder site or sites, it will take you a good six months to a year to see reasonable profits. How much you lose in that beginning period depends on how aggressive you are with the costly steps, but that also directly relates to how big the profits will eventually be.
So I hope this long winded babble helps some people see a clearer picture. As I said, I'm sure there are plenty of you out there with many intelligent comments to add. My experience is certainly not the only one. Make use of it for what it's worth to you!