@Joseph Johnson sounds like you have a great location and a flexible seller so it has the bones of a great deal. To put some meat on those bones I would definitely want to have an experienced Seattle multifamily development specialist on my team. Your friend might be a great builder but I wouldn't want to bet $2.2M that he gets his first multifamily project in an unfamiliar jurisdiction right the first time out. Not knocking your guy but having done similar projects in Seattle in the past (even though growing up there and owning a construction company) we saved our you-know-whats by having a development specialist to guide us through the labyrinth that is the City of Seattle.
The other thing I would do is really drill down on the numbers starting first with the construction costs. As a first time developer how much extra contingency is built in? Imagine you're hiring a first time developer and a non-local contractor... How much for increases in labor and materials between now and when construction actually starts? The surprises in those things are always on the higher side.
The other numbers to really dig into are the rents and expenses. If lease-up isn't going begin for a year or two what are the projected rents, vacancy and months until stabilization based on and how will the market have changed between now and then? On the expense side 30% of GOI looks low, not saying it can't be done but I would definitely want to verify those assumptions with research from someone besides a broker. Even if it costs a couple thousand, that's a rounding error on a $2.2M project.
One other consideration is that developers earn their money the hard way, with blood, stress and tears... and more stress. These projects require significant amounts of time and energy even for experienced hands so add your learning curve on top of that commitment to figure the non-financial part of your investment in the deal. If that and the numbers add up, go for it.
I have a number of contacts that may be a good fit for your project that we can discuss offline if you'd like.
Good hunting-