1) What is the "backbone" of every RP server?
For now, the over-killed backbone for every RP server is start with nothing, get a job, car, house, and join a faction. Honestly, for me, that's extremely boring. I would suggest making a theme to base everything in your server on. This would make changes to the whole RP style of play. For example, if you had an RP based mainly on criminal activity. Have a huge majority of the details go into that part of the script. Make multiple gangs/factions, have very specific details go into each. Like when someone wants to join the gang, they have to go through a recruitment process and/or accomplish goals. When they are finally let in, they will build the ranks. While all of this is going on, have the usual jobs, such as trash man and taxi implemented. However, when the trash man goes to pick up the trash, he has to get permission from one of the gang members to enter the vicinity of the gang's property, assuming one is online. I'm sorry, but is that the type of answer you were looking for? Either way, remember to have some type of theme to go along your mode. You could even have a documentary before the player registers. For the example of mode I provided above, you could have information by a once peaceful city that was overrun by large groups of criminal activity, once ... and continue the story.
2) How to maintain a good balance between paychecks and prices?
Just try and make the prices as realistic as possible. For example, don't make a decent sports car only 5k dollars. I understand that it would then take a long time for people to even get a crap car, but you could introduce leases and buying used cars. As for things such as food, once again, keep it as it is in real life. And add ways to earn money other than just the job. How do people make money in real life? Cutting their neighbor's lawn, making a website online, etc. Use your imagination and come up with something completely unique. While I'm on the track of realism of money, you could also implement things such as cent to the economy. Instead of a burger being $4, you could make it $4.55, etc. It would also be neat to allow players to have their own currencies. Grim_ released two scripts a while back designed for those two ideas specifically.
3) What make a server succesfull/popular?
It's hard to get players now days, which is really a shame. People go to the server that is already the most popular, it's just the way things are going to go. They're also afraid to try new things. If there was a new video sharing site, do you think people would instantly leave ******* to try it out? No, obviously. You need to really spark their attention at your advertisements and their first appearances to the server. So, when they connect, you could move away from the standard class selection and move on to a camera roaming the city, while they choose their password and player details. Also use textdraws to fill in information about the character, not standard dialogs. (Credits to Hostile Core Roleplay) Seif made a registration system some time ago that would work great at showing how you could make text fields do-able without dialogs. It would require a lot of extra work, but that's what would catch people's eyes, so honestly, it would be worth it.
4) Dynamic housing/businesses or static, pre-made? Which one do you prefer?
It wouldn't really matter what we (the average player) would like to see, unless you plan on use making houses in-game. What would you like? What would be better for you as the developer of the server? Would you like to create houses in-game, or are you fine with just adding them to the database or text-file when you're offline? Also note that dynamic systems usually take longer to construct, so if it's not worth the extra time to you in your development, don't worry about it.
5) Linux or Windows? Which one is faster and more reliable?
Either would work perfectly fine, really. People seem to favor Linux as it's slightly more dependable and secure. However, you can get a good host running Windows, such as KingJ, too. So don't count Windows out completely!
Hope I helped and got the main gist of what you were looking for with those questions.
