You have this cool client that has this really great idea, and they want to turn it into a sure thing.

They approach you about joining their start up, and they have money sticking out of their pockets, just waiting to be given to you as a (gasp!) full-time employee where you can enjoy in the fruits of their idea that’s going to stop traffic and replace sliced bread as the next great invention.

As soon as you take off the rose-colored glasses, start ups are not all they are cracked up to be. I’ve been connected to a few of them, and they are your basic kill-your-own, do-it-yourself places where nothing is set up correctly, from the office cubicles down to the process of developing software. If you need structure, this isn’t the environment for it.

Here’s a few things I’ve learned over the years, some of them I learned by turning down jobs, some I learned through painful first hand experience. Start ups can be rewarding, at least what you learn, and maybe financially. Here’s a few tips.

Make Sure They Have Money

Very few businesses make money right away (we’re talking one in a million), so there needs to be some runway time to execute the idea. Whatever money they have, they probably need double to do it right, and most venture capitalists intentionally don’t give start ups enough money just to see how resourceful their management is, or to see how dedicated they are in making the idea work.

Make Sure They Have Money To Pay You

What that means is even if they have a decent sized budget, if they are offering you the low base salary and the high percentage commission or bonus (or a high number of stock options), the start up probably doesn’t have enough money to pay you.

If you do decide to join a start up with a high upside, get whatever agreement you have with them in writing, and pay for a lawyer to review it. Have them poke holes in it, just to make sure that you are going to get rewarded for your time, because you are going to be spending a lot of your time on their idea.

If they offer you something low, and they’re not going to show you a list of what everyone else is making, there’s a good chance they are low-balling you.

Make Sure That There’s A Market For It

There’s nothing worse with coming up with this really great idea, and there’s no market for it. Or they come up with this really great idea, and the market’s too crowded. Or they come up with this great idea, and you have three friends that have worked with start ups that have had the same great idea, and all three of their start ups have failed for the same general season.

Unless you’re Apple (and let me tell you, the idea for the iPod was not original), there are no more original ideas, just a twist or two on existing ideas. Having competitors that are profitable in the market is a good thing, because it proves that the basic idea works, and can make money.

Make Sure The Idea Can Work With A One Percent Penetration Rate

Really, really, really big ideas take really, really, really big bank accounts, so whatever idea they have should be reflected in the amount of money they have to spend. Even if they have the money to spend, there should be some thought put into, “will this idea work with a smaller market penetration rate.” If it can’t, or you don’t think the company can be made profitable if their penetration is half of what they are projecting (and they should be doing some market research, regardless), it’s time to run the other way.

There’s no shame in working for a smaller start up that’s poised to be a double instead of a home run, especially if the team is smaller, and you see a larger portion of the riches.

Make Sure The Team Can Execute

Look at the team you’ll be working with — do you think they can execute? There’s nothing worse than working for a startup that has a few people that just can’t get it done, because that affects everyone’s bottom line. Additionally, most startups have friends of the founders they wanted to give jobs, but aren’t qualified to do those jobs. If you don’t think the team can execute, it’s not the right startup for you. There’s always the good first impression, but be realistic: can they get the job done and ship product?

Make Sure You Share Their Vision

There’s nothing worse than joining a start up, and finding out three weeks in you share a completely different philosophy than the founders. And you know what? No matter how much you are right, it’s their baby, and until the VC’s come in and replace them, it will still be their baby. Like any corporate environment, if you don’t share the vision (read this account of what’s going on over at Facebook), you’re going to be uncomfortable the whole time.

When you’re uncomfortable, it’s worse when you are working 60 hours a week, trust me.

At the end of the day, it’s just a job, maybe one where you can make a lot of money, but the reason they want there is that you can make a lot of money for them, and it will only flow downhill if they value your skills.