You could buy a super super cheap soldering iron online or you could get a moderately cheap one and save yourself a LOT of frustration. Trust me. Get the moderately cheap one. Weller is a good brand.

NP! I have the older analog temp dial version of this guy. A little spendy but not over the top. Uses common tips and from a good name in the business. There are a bunch of good options out there of course. Much better then a loose iron that just plugs into the wall.

https://www.amazon.com/dp/B077JDGY1J?ref_=cm_sw_r_cp_ud_dp_FXTBTVE1BR4EN33ZX5V9

https://www.amazon.com/Weller-WE1010NA-Digital-Soldering-Station/dp/B077JDGY1J

Also spend the money and buy a kit of different size good quality tips. Like... https://www.amazon.com/Weller-Screwdriver-Station-Soldering-Desoldering/dp/B071KJ5Q2Z/