No matter where you buy from, renewal price is more important than sale price. You can buy domains for less than $5 /yr for first year or sale period. But in those cases, you also need to check the renewal prices.
Also, you are allowed to purchase only one domain at a time from one account for such offers, if you trick by using different email ids, still there are chances for registrar like Godaddy to find out about you.
So my suggestion is to buy from a cheap domain registrar, that offers cheap renewal and buying price. If you want to save for first year, you have to try 10 -20 domain registrars or resellers and buy from them for cheap and then transfer to namesilo at the end of the year.
I am not sure, if you are able to find offers and you should also check their terms and conditions. Some companies charge transfer out fees as well. Check everything, if you want to keep domains for longtime, i would suggest namesilo for cheap buying and renewal rates.
Thanks