Ask HN: What do I need to do to prepare for incoming investment?

My co-founder and I have been bootstrapping a project for a few months. We have basic functionality in place and current expenses are low and are offset by the occasional freelance gig.

Recently, we have interest from someone for an investment in the low six figures range.

This is uncharted territory for us, as we usually just do our best with what we have. The terms of the money are favorable, but I do have a few questions:

1) What should we have in place, corporation-wise, before accepting the money? LLC? C-corp? Unincorporated?

2) Probably quite the newbie question, but are there any tax burdens associated with handling such things? I have a consultation set with an accountant/tax person in a few days but wanted to go ahead and get an idea of what I'm looking at.

For those of you that have received such investments and/or offers, what did you do and how did you handle things?

Apologies, as I am sure this has been answered before, but my late-night searching turned up nothing.