amazon niche website question

i found a site that seems pretty legit ( i think) HPD. IT sells amazon niche websites built around niche keyword the company researches. basic sites r about $500 no domain and the aged sites 6months plus old with ranking for 1500$ my question is can i just buy a good aged domain slap it on the 500$ new site so i can start building links immediately? the 1500$ site is real nice but its hard to justify spending the extra money if i can simply buy a domain aged so i can skip the new site sandbox period and start trying to rank the site.