You can look in the Denville, Rockaway, Parsippany areas to be close to Mountain Lakes. If you don't mind a little travel time (15-30 minutes) then the options really open up. If you would like to see what is available in your price range, email me and I will send you properties that would meet your needs. I am a realtor in Fairfield (which is east of Mountain Lakes) but I do service these areas. I can also be reached by phone at 973-575-6353 ext 21 or my cell 973-632-4644. My email is firstname.lastname@example.org.
Good luck with your search for a home !!
To be honest, while you can find something in Denville at that price, it's going to be something that needs work, or something with locational issues, or perhaps something on the very small side.
You might want to open up your search to Rockaway (next town over) and consider something like White Meadow Lake. You might get a little more for your money and it is a nice community with a beach, very convenient to highways and shopping, and easily driveable to a train station for commuting.