I would buy one from a reputable industry trade site. Cuccio as of September has an offer on their mini led lamp, which is fantastic for toes and nails. It says its a five finger cure, but I do four fingers then thumb. There's no timer on it, but I just use the timer on my phone. The deal is not listed online but you can call them up to set up an account, which they will do so after you have emailed your certificates over. I obviously can't put trade prices on here, but it's a steal
Only if your manufacturer recommends it. Otherwise it can cost you more in lost customers (seriously). Especially with LED, the UV emitted is in a much narrow spectrum which makes it that much more important to ensure the right match.