how does a house become old row?

It's not bud light, it's Budweiser and having a majority of in state girls isn't what makes a sorority Old Row, that's just what is common for already Old Row houses to want the in state girls more. If I'm reading your question right then a house can't really "become" old row if they aren't already. I know Phi Mu didn't become Old Row until the 1990's but that was huge exception and I doubt something like that will happen again, at least anytime soon.

There are a few houses that are allowed to be old row but were not allowed to be sponsored by Budweiser at the time. Old row is no longer sponsored by Budweiser and being on old row has to do with when a chapter was established.

First, sororities are not old row or new row only Fraternities are. There is this misconception that there are old row sororities based on they have a strong partnership with old row fraternities and get invited to the big old row party.

Old row is simply a handful of fraternities whose original houses were on University Blvd and stayed there when other fraternities moved to new row (Jefferson). Back in the 1950's all the fraternity houses were all around Bryant Denny Stadium except SAE and KA which were on the other side of campus. The university offered all the fraternities the opportunity to move to Jefferson with bigger houses than the old ones around the stadium. They all moved except what is now called old row houses.

This eventually turned into a once year party for those old row houses which they invited certain sororities to be part of. Mostly this affiliation is based on the sorority membership came from the same areas of Alabama that those old row fraternities focused their membership recruiting.

Sorority row was actually 3 cul-de-sacs where the current sorority row sits, so you will hear some people refer to certain sororities as First circle as their houses were the first built on the first cul-de-sac to be completed. The only remnants of that is the intersection right in front of the KD house.

Here's what I've been told: A certain number of sororities and fraternities are "allowed" to pay money to have this big blow-out party. If a group drops out, the other members will invite a new group to take its place and attain "Old Row" status.
Of course, the terms almost immediately started bleeding over into tier designations.