Possibly a beginner question?

Sorry this may be an obvious answer - typically I do local service based business, this project for a friend and I is a bit out of my norm. I am Building a lead gen website - have a primary domain. I am purchasing 4 or 5 variations of said domain that target more specific areas of the general niche (automotive - more specific domains have keywords related to specific services). Better to have all redirect to primary domain, or build out multiple websites? It doesn't matter which "site" they land on, all sites will have same shared clients purchasing the leads. Eventual goal is entire United States, currently set up in single state and have built city pages. Expanding to 3 states in the next 3 months and want this structured right from the start. 2 biggest reasons for asking / why I'm torn - 1) SEO- separate sites will steal juice from each other, but could dominate top of local search 2) Paid Ads- can advertise 5 separate domains for search ad, but couldn't advertise a bunch of redirects in search ad Thanks in advance!