This question was asked previously by another person. I don't know why some people (mistakenly) think that they'll have to pay a monthly fee with the ZTE. Maybe Tracfone had a confusing advertisement. There's no monthly fee required, either initially or later. You just buy additional time when your units or service days run out.
When you're at some place from home that has wifi, like a restaurant or hotel, turn wifi on and the phone will find the new network. You'll need to know the ID and password to sign in if that network is secured. As for using 3G, you can turn it on and use it anywhere that you have cell signal. But use wifi if available, so you don't use up your data bucket.
No, you buy time cards which give you either 90 days or 1-year of service, and a number of talk minutes, text units, and data. This phone has Triple Minutes For Life (TMFL) feature, so the face value of the card will be tripled, a 200-minute card will give you 600 talk minutes, 600 text units, 600 Mb of data, and 90 days of service. Add another card before your service days run out and all the unused units rolled over.
The phone says "Total space: 2.34GB" for Internal Storage. I think that should be enough for most users. I have 70 apps on the phone, including what came with it and what I downloaded. Some of my aviation/navigation apps have large map databases. Even with all that, there's still 1.51GB of free space. The bar chart shows I've used only 1/3 of the internal memory.