Hi @Leah Bates, I think knowing what the numbers roughly will be, would help the decision as well. How much more is your mortgage on the duplex going to be vs. your current rent? Moving into a duplex without a tenant might be a negative hit to your cash flow, but I'd guess that it would likely be net positive change for you overall (in terms of total net worth) once you consider the equity you're building instead of paying someone else rent (plus all the tax benefits and everything else that goes along with home ownership).
If you absolutely couldn't financially handle not having a tenant for a few months, then maybe wait, but I'd be surprised if that were the case. I was just listening to one of the recent BP podcast episodes where David just answers questions and he was talking about how it's worth lowering the rent a bit to get someone in sooner than having a vacancy for even a month. Lower the rent $100-200 from where you would ideally want it, then just raise it up next year when they go to re-sign.
Also, I just want to acknowledge that I know it's a huge pain to break a lease and have to pay your landlord an extra one or two month's rent. I did it in 2019 and hated giving up that much money, but it was definitely worth it. I'm not sure if it is, but don't let that hold you back if you can afford it.
Hope this helps!