Budget? Hmmmm.....well, when I thought about getting back into roasting, my first take was that the Behmor would be just fine at $300; that's an amount that I'm okay spending. If I am going to be miserable with anything that costs less than the HT ($800), then maybe I'm still gonna need to revisit building again (or paying someone else to build for me.....).
I pull one or two double shots a day in my Gaggia Classic -- for lattes. I use about 12 oz coffee per week. I have two decent local roasters from whom I can buy freshly roasted, dated, espresso blends (Flying Goat and Ecco), so roasting isn't a matter of survival.
Why would I want to roast again? Hmmmm....maybe just so that I could have more options than the two good locally available espresso blends and for the satisfaction of doing it myself.