@Justin R. - I only have the details you've posted so forgive me if I'm missing something here: From my perspective, you've got some serious digging to do. I applaud your ability to see a problem and want to adopt a solution. That's very entrepreneurial of you. But with that being said, here are some serious things you've omitted in your evaluation process that could drastically affect your budget:
(1) As others have mentioned: ZONING. This takes Legal (land use attorney) + depth of Architectural experience. It doesn't matter what your budget is if you can't even get the building approved for it's the new, intended use. Some zoning laws are antiquated and you may have zoning regulations that are unfavorable to this type of housing. If you haven't spoken to someone at the planning office, that's the best place to start.
(2) It will be hard to estimate costs for construction until you understand what the change of use will trigger; here in Oakland/CA it triggers structural upgrades, fire upgrades, electrical, etc. Understanding this can be the make-or-break on a project.
(3) You need a GC/architect who have worked together before and have a good working relationship. They need experience in this space (adaptive re-use or work with commercial interiors) This can also come in the form of an integrated design/build firm. This will save you time and essentially, holding costs.
(4) I'm not sure if you've considered this but any time spent on entitlements, zoning approvals, etc. just to start construction will have no only soft costs associated with it, but also holding costs from your lender. You need to factor this in as it can have a very negative affect on the returns of your project. If you're bringing in outside investment, this will also put you at a disadvantage to other investments that pay right out of the gate. So there has to be significant upside on the back-end through a sale or refinance.
Sorry if you've considered all the above and this was repetitive. Hope this helps. Last thing I'll mention is operating a co-living property is very different than living in one. Property Management is HARD. Being an operator and a PM is MORE difficult, IMO. I would seriously consider finding an experienced operator to help you out of the gate. It's a lot of heavy lifting for just one person or even a team of 2-3 to handle.