I raised about that much. We were farther along though, we had 3 founders, 200k in ARR, 300% YoY growth and our projections were to hit 1.5m in ARR in 3 years. Angels we didn't already have relationships with were not even remotely interested. (The ones that did invest were friends). So we were only able to raise from friends and family.

You said you were willing to part with 40% at a 1.5m valuation for an idea which is a very high valuation unless you have a very particular background, or a track record of building successful companies (which I assume you don't have or you'd have the cash or network to fund it). A company with 300k in ARR is maybe worth a million dollars. Do I want my 50k investment to maybe be worth 33k in 3 years IF everything goes according to plan? In addition I don't know how you're going to make this work. If you have a burn rate of 400k your first year, and aren't going to be profitable for three years how do you make 600k last until you hit profitability?

Companies like this with small dreams are mostly bootstrapped with a little money from family or friends (Note you will very likely some or all of this money, keep that in mind when taking money from family and friends). Given you constraints this is realistically your only option. And if you want to accelerate how quickly you go to market find a cofounder.