The rule you are referring to is probably 37 CFR § 1.29(a)(4), which provides:
Neither the applicant nor the inventor nor a joint inventor has assigned, granted, or conveyed, nor is under an obligation by contract or law to assign, grant, or convey, a license or other ownership interest in the application concerned to an entity that, in the calendar year preceding the calendar year in which the applicable fee is being paid, had a gross income, as defined in section 61(a) of the Internal Revenue Code of 1986, exceeding three times the median household income for that preceding calendar year, as most recently reported by the Bureau of the Census.
"Ownership interest" relates to any kind of proprietary rights that another party might have over the patent application. Part ownership is the most obvious form of ownership interest.
Thus a translation of this into simple non-legal English might be:
The applicant or invention has not given (or promised to give) rights to the patent application to someone else, if that person earns more than 3× median household income.
Would Kickstarter contributions count as an ownership interest?
It seems unlikely, but it depends precisely how your Kickstarter campaign is set up.
If backers are given 1% ownership in the patent, or shares in the company which holds the patent (or something like that), then they would have an ownership interest in the patent, and would need to comply with the income requirements. It seems unlikely that a campaign would be set up like this though.
However, if the backers are given a copy of the product (which may or may not be patented, it is irrelevant), then they will be receiving no rights over the patent application itself: they simply get a good. This is therefore not an ownership interest.
What if my entity status changes?
That is fine: you simply need to notify the USPTO before or while paying the next fee (37 CFR § 1.29(i)). You will then be paying small or large entity fees (depending on the situation).
If you pay a fee at the wrong rate, this may be considered fraud (which could result in, among other things, an invalid patent) (37 CFR § 1.29(j)). However, this may be remedied if the mistake was made in good faith (37 CFR § 1.29(k)).