Glad you like the mod and welcome!
1: The repair costs are the same, even if you have heirloomed ones. The chance of it breaking depends on other stuff tough (check other posts)
2: Yes, making money while having the top tier equipment will eat all your money. What most people do is grind a bit so they have a cashbank (about 30k will be fine, 50 if you want to be even more safe) and then play with a setup that will have a even income/gain relationship. This used to be considered around 35k, but some can have it up at 50k because they are good at making people use teamwork/play with a clan that usually wins the round.
Having a setup of around 20k in the beginning will get you your gold reserver ready. Move then up to 35k and see if you lose/gain/brake even in the long run and then go up, down or stay the same. If you stay on foot and use medium equipment you can still get 20-30k in total setup so you wont be that underpowered in the equipment area.
3: Couchable means you can couch a lance, i.e. hold it down while you gallop. The way people do in tournaments for example. This is an attack that can't be parried (but can be blocked with a shield) and does very high damage, most of the time instantkill.
In SP you can do this automatically when you have high speed, or if set to manual, when you press x while having high speed. All MP servers (or at least all I have played on) have couching (and parrying) set on manual.
4: The higher the speed rating the faster the weapon yes. Altough remember that some people will hit you first even with a slower weapon because they have a higher agility and/or wpf than you. They can also do it by using footwork (placing themselves in a favorable position) so that they will hit you in the earlier part of the animation, thus hitting you earlier.
5: The best lances are the Heavy Lance for reach and damage (BEWARE: This is a REALLY slow weapon. The slowest melee weapon in the game!" and the Light Lance for speed.
For a heavy cavalry polearm/1h/shield I would take the Heavy Lance. This is only if you have any wpf in it. If you want to couch and have 1 wpf in poles then you should take one of the couch only lances, like the Jousting/Great Lance and use them.
The Great Lance is your best bet then, since it is the longes lance. (BEWARE: the jousting/great lance cannot stab nor block, only couch. Thus they are useless on foot or if you are caught unaware. Only use on horseback, preferably with a shield.)
Here are some versions of the builds you asked for.
Horse crossbowman:
Horse crossbowman
Level 30 (4 420 577 xp)
Strength: 15
Agility: 21
Hit points: 50
Skills to attributes: 2
Power Strike: 5
Shield: 7
Riding: 7
Horse Archery: 3
Weapon Master: 7
One Handed: 140
Crossbow: 110
Swap the wpf if you want to.
The "Tank" Heavy Cavalry
Level 30 (4 420 577 xp)
Strength: 21
Agility: 15
Hit points: 70
Skills to attributes: 2
Ironflesh: 7
Power Strike: 7
Shield: 5
Riding: 5
Weapon Master: 5
One Handed: 148
Please take note of the sweet, sweet 70 HP. They are lovely!
PS: All these builds are for pure cavalry. You might be better off with a cavalry/footman hybrid and get some athletics. 0 athl can be very slow when you lose your horse.
6: Too long.
That's what it takes.
Of course this all depends on your multiplier, but if you aim for a lvl 30 build and not 31 then you will be much more happier. Just saying...
