Never apply to jobs like these, for several reasons.
1. The client either doesn't know anything about the area they need a hire for, or they are just too lazy to write out a detailed job description to find a good candidate. You don't want to deal with either of these, for many reasons that I could write an entire book on.
2. If you don't have specifics, how are you supposed to input a reasonable bid? For example, if a client leaves out what the word count is, how are you supposed to know if their budget will cover your time worked?
Just last night, I broke my own rule of not applying to jobs like these, when a certain subject caught my attention and I applied. The job posting made the project sound like one article for $30, but when I got a message back saying the company would like to hire me for a 5-7k word guide, I had to decline because $30 would never cover that amount of work. Vague posts will only waste your time in the end.
3. It's easier for clients to scam contractors with job postings like this, because the descriptions are so vague. This leaves a huge amount of room at the end of the contract for clients to say they were unsatisfied with something, ask for a refund, or refuse to pay if it was a fixed price contract.
I'm not saying all clients who write descriptions like this do that, but it creates the opportunity to do so and you don't ever want to mess with that. But you can weed out your chances of getting the clients like that by applying to jobs that give all the details. Good clients always write a description that tells the contractor everything they need to know to bid correctly.