Anyone can apply for a second mortgage even a person with a bad credit history there are absolutely no limitations. The lender will see your debt income history and your work history to decide about the amount that can be lent to you .If you take the help of a broker then he will try and reduce your high interest charged by the lender. A broker will also introduce you to many lenders thus making a wider choice of lenders available to you.
Second mortgage is good if you want to make some necessary improvements in your lifestyle and if they cost more than your ready savings. Second mortgage helps in getting you money on your house which is already in mortgage. So it is an additional loan taken on your already mortgaged property but through a different lender of course.
Interest rates are higher on second mortgage loans because the lender has to safeguard his interests since the property he is investing in is already mortgaged he will have secondary rights on it while recovering his loan.