HU is awesome.
Also you CAN beat the rake; you're just paying 5% rake on flops seen same as any 6max or FR player. It's just everyone insists on seeing flops too wide HU so that you end up flopping garbage all the time, and playing just above breakeven EV even if you're good. YOU DON'T HAVE TO OPEN EVERY ****ING BUTTON.
A balanced preflop range HU would be 33% open, 33% defend vs minraise, and 25% defend vs 3x (just enough that villain cannot autoprofit from raising every button or folding every BB). I would actually recommend 3xing 40% of buttons, because it actually gives you room to make some money when villain folds (when you open 33% you're breaking exactly even on every BB fold) so that if he's actually tightening up to adjust you can have some more maneuvering room postflop since you're actually paying less to see the flop than he is.
Also there's literally no excuse for playing looser than that preflop. It's not like 6max where if you play nitty the only way to get proper volume is to add more tables; you're the only other guy at table. If you decline to see a flop the flop's just not gonna get dealt, and open-folding just adds 4 seconds of play time. It's one thing to get laggy and **** with people postflop, but seeing flops too wide is just costing yourself money, for no reason.
So, in a vacuum, my recommended preflop ranges are as follows,
IP:
-40% open
-14% flat 3bet (depending on 3bet sizing, if Villain is opening big you can defend less)
-6% 4bet
-3% call 5bet jam (basically just QQ+/AKs)
OOP:
-34%/25% defend (Minraise/3x)
-16% 3bet
-4% 5bet jam (TT+/AQ)
Flatting 4bet is not recommended. Playing OOP against a range that tight gets ugly fast.
Depending on ranges and dynamics you can 3bet/4bet/flat 3bet/etc. wider or tighter, but I don't recommend deviating from the standard open/defend range.