The lean startup methodology teaches customer development over product development, yet everything here is talking about product development.
Two things to quickly note:
1. Everyone says they use the lean startup approach
2. Very few people actually use the lean startup approach
Does the product have to launch in 18 months? Can you show your progress to the next round of investors and get more funding that way, without a full scale launch?
Paid marketing should be one of the last things you do. Paid marketing is meant to put people into the top of a working marketing funnel. There are other ways to get your first few hundred customers that I would recommend before paid. Blogging, Social, word of mouth, and doing startup speaking, etc.
I would also recommend finding your first customer before writing one line of code. Go to the mall and ask around for people looking to travel (or whatever specific niche you are in), give them your value proposition, and judge their reaction. If you are B2B this is a little bit harder, but you can still do it. This will save you $100k. I am not exaggerating. And yes, peddling at the mall is slightly embarrassing, but telling your angel you just built a travel site for mice (or something else that flops) is much more embarassing.
As for equity, it ALWAYS depends. You got $100k, you are the original founder, that's worth something. Would your technical co-founder be forming the concept of the business, or would he really be "employee #1" but with a larger role than your real employee #1?
Think of it this way, if he put in $100k and worked side by side with you to develop this, he should have 50%, right? At least 40% I would think. Who had the original idea, wireframes, and forming a business entity barely account for anything. If you tell me, "Well, the idea is worth 5% alone," then I would tell you, "OK build the entire business yourself and keep that equity," and when you can't, you will see why the idea is worth nothing, the execution is worth everything... Unless you have a patent on the idea, but most ideas are just ideas, not patentable products.
So back on topic, you have to get the tech co-founder on board with the concept and the idea of not getting paid for a while. You have to sell your business to them! That's the hard part.
After that, I would offer up a large chunk of equity, vested over 3 or 4 years (same as yours). Maybe 10-25%. And of course if they are the other half to the business, you both accept that that equity will become diluted upon hiring the next 10 employees, etc.
So the "founding" team might look like:
Co-founder #1: 25%