To echo what the other guys have said, the amount is very variable and depends on the local market plus any Tenant Improvements ("TI's"). It's negotiable with your landlord. I'm not sure how useful this info will be to you but here's an example lease for my zip code. Note the built-in rising rate. You can expect your landlord to want to increase rent along the way. I doubt any owner would want to keep rents at what they were 5-10-20 years ago. Also, this space represents (probably) much more square footage than a new solo practitioner would need the first few years. Depends how busy you get.
Months 1-12 $5,679.10 per month ($1.90 PSF PM)
Months 13-24 $5,858.44 per month ($1.96 PSF PM)
Months 25-36 $6,037.78 per month ($2.02 PSF PM)
Months 37-48 $6,217.12 per month ($2.08 PSF PM)
Months 49-60 $6,396.46 per month ($2.14 PSF PM)
CAM CHARGES (Cost of Area Maintenance): $1,614.06 per month ($0.54 /sf/month estimated)