I think that your first and best resource is your brother in law. Make yourself a list about what you hope to do in cycling and talk to him. Until you figure out how you want to ride you won't know what sort of bike you need to research. You have a generous budget, but if you have little ability to assess the mechanical condition of a second hand bike you might be better off buying new unless you can enlist the help of a more experienced person. Brand names are not useful unless you are familiar with specific models within that brand during the year that particular model was produced. This makes buying second hand a bit complicated. The other thing about second hand bikes is finding the correct size. There is no sense in buying a size small of a particular model if you are tall enough to need a size extra large no matter how good the deal is. At least, buying new allows you to specify the correct frame size when you purchase from a dealer. Knowledge is power. The more you know about how to assess the condition of a second hand bike and how to select the correct size and to read the specifications of that particular model the better placed you will be to tell if the asking price is fair. In my experience, the asking price for second hand bikes is too high more often than not