Manila rarely looks at the I-134... They never looked at mine or any of the friends Jaycel made there at the embassy while waiting for her interview. That being said, it is good you are looking ahead to be prepared. Your Gross income is what will matter. For historical trends in income, you will provide Tax Return Transcripts from the IRS that will establish that. For current income (which is King as @SalishSea mentioned), 3 months of your most recent pay stubs will suffice and a letter from your employer stating that you are a regular, full-time employee at (x) Rate (either hourly or yearly, including any regular OT) is fine. If you have $50K gross, and it's just you and your fiancée, it will be fine.