comments:
The cheapest way and best way is just to buy a long enough ethernet cable. It's uglier but you will achieve the max speed possible without spending much money. A single 100 foot Cat 6e or higher cable is anywhere from $16 to $30 depending on the brand and cable appearance. If you do down that route, just be sure to have a really good guesstimate on the total distance of the cable route when it has to go up and down door jambs and around corners. New routers will cost you a bundle. A tri-band will probably be over $400. A dual band will be over $100. Both will depend heavily on placement and your current pc hardware to achieve max speed whereas the ethernet is ready to go. Powerline adapters will be cheaper but depend heavily on how your apartments electrical wiring is setup as well. Powerline adapters will be quite cheap relatively speaking, almost equal to good quality ethernet cabling but can have some performance issues with noise on the electrical circuits. Another good alternative is MOCA adapters for locations with coax cables. If the coax is able to be connected internally in the apartment, you can use existing tv-style cable runs to connect to the router. However, this requires full knowledge of what cables connect to where in the apartment. Sometimes this is problematic in older homes/apartments that have had a lot of changes. EDIT : if your closet abuts his closet, I'd cut a hole into each closet wall and attach a wall plate like this : (and attach 2 ethernet cables on each side and a short 1 foot ethernet cable in between. It'll look like it was planned for and looks tidy enough for inspection. Doesn't cost much and most people will never even notice it. https://www.amazon.com/dp/B0DS1QBKNG/