Is there any way to get money without buying it?

First Question: Get a job. If you're over 30 days old, try a club or 3 as a dancer, host, escort, DJ, etc. Tell ya what, if ya contact me in-world, Ill help ya out, I help newbies all the time. Contact Amayathyst Hannu.
As for becoming mermaids, mermen, etc, do searches for Mermaid and Merman avatars. Theres bound to be loads of places. Weapons, it depends what kinds you want, theres loads of assorted weapons all around SL. I wouldnt recommend using them, unless you're RP'ing. Most weapons can get you banned from SIM's. If you're RPing, make sure that the weapons you use are compatible with the system you use, such as CCS, DCS, Gorean Meters, or PC. If you use weapons that arent compatible with those systems while you're RPing, you'll be labeled as a griefer and ejected/banned from that SIM.There are no cheat codes to get money, either work for em, go to contests, or buy em with a credit card.

Happy Hunting!
Amayathyst

I found noobie area junk yard has some weapons and cars I would like to get money other than zone camping too

There are numerous freebie areas in second life. There are probably some merman and mermaid costumes somewhere. My best way to get money is hoppy pay it pays you for teleporting. Oh yeah one more thing the elemental is a really cool vehicle. It has a coupe, a motorcycle, a hover car, helicopter, airplane, air ship, boat, and submarine.

There's as many ways to get money in second life as their are avatars. Depending on you, you can either go clubbing (events usually have big payouts), go camping (boring, wouldn't recommend it), start making things and selling them (sl exchange or onrez are some great online resources for marketing your second life creations), get a job (believe it or not, they actually exist. But if you really wanted to work, why do you have a second life?), or by far the most popular start selling freebies you can find anywhere (someone's bound to buy them eventually, though it's not exactly ethical).

no cheats,work hard,or easy.the hard way is a regular and casual job like:work at a grocery or..well that's the hardest XD.easiest way:simply become a host at your local hangout club,if you like talking to people,you make friends and get the party going.pherhaps be a DJ and change songs after a while or and get tips,ask people to tip the other staff and while the others will ask to tip you!
or.....be a dancer or stripper.
another way is start a buisness.ingame,i'm niko farlight,i started a shop along with luke whitewood,not anything fancy though.
OR...buy it with real US$ by lindex,or change membership to premium and get 1000L$ AND YOUR OWN LAND AND A LINDEN HOME.through credit card or paypal,believe me it worthes best!
End Of Session.

If you are looking for free stuff if you go on the seconflife marketplace theres lots of stuff but remembe to set the relevence to price:low to high