about second mtg

i have 80-20 mtg on my home. my first mtg is 310,000.00 and second loan is 65,000.00. total mtg is 375000.00. home in my area are selling for 270,000 to 280000.00. we are not paying on our second mtg for past couple months and they send us another offer for 52000.00. still we can not afford it. we want to stay in the house if we can, only reason is that our first mtg modification is great. is it advisable not to pay on my second mtg and just continue with my first payment on time? we had thought about doing a short sale only if we have to, since we are so much minus in our equity and property tax is 9200.00. Also what can happen if do not pay on second at all? let me know. Thanks