Or go for 1 x 16GB now and expand later.
But yes provided that your motherboard can accept 16GB sticks you should be able to run 1 or 2 16GB sticks giving you 32GB or 48GB.
Having said that it is a lot easier to get matched RAM, otherwise you may have to manually adjust bios to the lowest performance numbers. there is a small chance that mismatched RAM may not play nicely, although in 20 years i have never had a problem.