Drastic had an unlocked Iphone 3 purchased on ebay for $50. 30-day 3G sim card was $2.50. Worked.
Dras helped me pick a Chinee throwaway flip phone (dual sim). Same 3G sim. Total: $18.50. Worked to text others in the group. Money well spent.
ftr, the ip3 sucks, terrible choice. Luckily was only 30 bucks and can resell.
Slightly OT, I just ordered a Project Fi phone, works on T mobile, Sprint and free wifi. Free to make/receive calls via wifi to USA from anywhere in world, if I understand correctly. 7 cents/minute to call Vietnam from USA. Nexus 5x is $199 if you try it out (normally $349) . Unlocked GSM so you can put a sim card from just about anywhere and it will work.
20 bucks/month plus 10 bucks/gig - any data not used gets credited each month.
https://fi.google.com/about/
I gave up on the tattoo and going for a permanent G grill.