i believe tethering is alowed with the new "no contract" plans. for $50 you get 500mb of high speed,but for another $20 you can get unlimited highspeed(4g and lte)
i personally would not want to have my phone be my source of internet. IMO its a hassle to set up everytime i want to go online,plus i tend to leave my PC connected 24/7,wich i could not do if used my phone to tether.
plus im sure i use more data on my home internet than you can shake a stick at,since im constantly downloading and uploading roms and ruus for various phones,wich are up to 900 mb a pop
i wouldnt want to put my phone thru that abuse.
if your internet needs are different,it may work ok for you,but the $30 a month i pay for DSL is well worth it to me(plus you can likely find faster for cheaper if you look)