I-864 tax return questions

[ta-anon 0]

I started working full time in the US in January 2007, before this i was a student. My 2006, 2005, 2004 tax returns all show incomes far below the poverty line (because i was at college and they were just part time jobs).

Since January this year however, I have been employed full time earning far more than 125% of poverty line and have a letter from my employer stating my income, job title, how long i've worked etc. I've also got pay stubs, bank letter showing savings. I was wondering, will they be put off by my 2006 tax return being so low, so should i get a co-sponsor? Also, where it asks for 2005, 2004 tax return incomes on I-864 should i put them, even they are similarly well below the poverty line? Would it help to include a letter explaining why tax returns incomes were so low (because i was a student)?