Per Ghost: "When i was a kid in the early 70's, i used to have a Fleischmann H0 railroad, sold since long. I've noticed an interest with my kids, and was thinking of starting all over again. But when i look now there's tons of brands, digital and analog, and I'm just getting confused. My question is, where to start? I do have many hobbies that eat on the budget, so cost is a factor (second hand is certainly an option)".
I started my layout 29 years ago because my two boys showed an interest. Having always been involved in some type of modeling activity, I thought this would be a good thing for my boys to get into. They've been out of the house now since the turn of the millennia and I am still very interested in the hobby. There is no secret to getting back into the hobby, just do it! I would recommend starting with Direct Current (DC); or, Analog as many call it now. It is the simplest way to get started and pretty easy to understand how it works. I ran my layout for the first 10 years as DC, however, I had always been interested the Dyna-Troll types of control systems that was available back when I got into model railroading. Around 1990; or so, Digital Command Control (DCC) came on the market and it didn't take me long to make the change. You can, if desired, jump right into DCC, this would simply be your choice. If you think DCC might be your choice, you need to educate yourself, by reading about DCC, before you make the plunge.
The ridiculous nature of this hobby is that you will start out with minimal knowledge about the subject and will need to make all kinds of decisions about stuff that you really need more information about, to make a good, educated guess. This is what we all must do, so relax, it seems to work out.
You also need to know that some people will try to educate you and it can be akin to drinking water from a fire hydrant! The information comes way too fast and there is way too much of it.
I am willing to help you and if you have questions, feel free to PM me.