Many times the Seller, current property owner does have a plat survey (an older one he/she was given most likely when they initially bought the property.... they or their Realtor may be able to provide you with a copy...
Otherwise there should be some lot size information at the county assessors office website...
Good Luck to you!
Edith YourRealtor4Life & Chicago Connection
Working always in the very BEST interest of her clients
Can you clarify your question(s) where a Realtor can assist you ?
Lynn911 Dallas Realtor & Consultant, Loan Officer, Credit Repair Advisor
The Michael Group - Dallas Business Journal Top Ranked Realtors