LyndseyRae

As for employment history.. be honest and factual.

Additional Information at VisaConnection_petition process
 
5 in the household.. are they all claimed as dependents on your mom's tax return?  If no, they are not included in the count.     Poverty Guidelines
 
USEM does accept co-sponsors with the K-1, but it is a case by case decision (much accept a qualified co-sponsor with the immigrant visa).  One thing the embassy does look for is the co-sponsor with the K-1 be an immediate relative, your mom is a perfect choice in that regard.

I moved your post to the Philippines forum for specific assistance from other folks who know the details of what's accepted and what isn't at the Manila embassy

For a household of 6, for AOS, your sponsor will need to make a minimum of $41,200.  The Manila Embassy will follow the guidelines set up by the Federal Government but they still can make their own decision based on the information provided.  For the K-1 it is a minimum of $36,960.

In the i-864 and i-864ez instructions (on the actual form)it states "If you were not required to file a Federal income tax return under U.S. tax law for any other reason, attach a written explanation including evidence of the exemption and how you are subject to it." As you had no income previously, you didn't have to submit tax returns and will need a statement saying why you haven't filed taxes.
 
Your mom can be your co-sponsor but she will need to meet the minimum income requirements for the household, including your fiance.
 
Also, you might want to look into your tax status - self-employed persons, depending on their activities, have to pay income taxes quarterly or they are fined. Make sure you're taking money from each paycheck and set it aside for those purposes. As self-employed or contracted, you will be responsible for the additional tax burden - normally the company splits the burden with you.