Inexpensive wireless solution

I'm 9 years away from IT but have been roped back in for a small business who would like to supply wireless to 5 different small businesses in their building, without sharing their network.  Can a few people offer up simple solutions so I can go explore, without trying to dissect all of Netgear to get up to speed again?? 
Also looking hook up a few hard wired connections into said wireless networks.  
I really did do a core dump on all IT when I quit my last job.   🙂   
Thank you for your time!
Pat