Liches are completely owned by a pair of EV's; Lich Lords go down pretty quick as well, although they occasionally dispel them. Although I can't remember the name of the dungeon (since I just use a rune), they spawn in large numbers in one of the virtue dungeons. Killing them there has the added benefit of giving you potential 'virtue artifact' drops; if you decide not to use them, there are some that can be sold for several hundred thousand gold each (such as the anniversary statues), and even the least desirable usually goes for several tens of thousands.
This is also a fairly quick way to boost Karma and Reputation; you can use the rep gains to do occasional rep sacrifices to boost your 'sacrifice' virtue which will eventually lead to the ability to self-ressurect up to 3 times a week. Quite useful when you are playing solo.
You can also do the aforementioned escort quests (someone pointed out they are 6k/hour or so); while I would suggest the Liches are a much quicker way to gain cash (as well as the other benefits), you should try to do at least 5 'rescue' style escorts per day to raise your compassion. (Rescues give a higher 'compassion' return than standard escorts.) Higher levels of compassion will make those you ressurect start with higher HP totals - always handy in group fights. You can quickly pick up 5 'rescue' escorts in a row by rescuing the prisoner in the orc caves; using gates you can pop out and back in fairly quickly and be done with the whole set within minutes.
I noticed your template is melee oriented; you might consider picking up Bushido. It offers some fairly powerful returns. Keep in mind, though, that Bushido is geared towards a 'no shield' build; at higher levels of Bushido you will actually parry worse with a shield.
With respect to vendors, there are several websites out there where you can search for items to get an idea what the going rate is. I have a few caveats, though. First, I do not know if it is considered appropriate to advertise such sites here (since most also include a link to, or are run directly by, gold sellers) so I will avoid posting the links. Second, it seems that the prices are focused on the Luna vendors which are generally higher than the vendors you will find elsewhere; thus, if you don't have a vendor in Luna you'll likely be unable to command prices quite that high. Getting a vendor in Luna isn't difficult at all - however you will end up paying a weekly fee to the person who owns the house, so if you don't have a large enough income you could end up losing money.
If you can find yourself a guild that hosts vendors, you can benefit from this by putting one of your own vendors in that house; some guilds offer free (or sharply discounted) vendor positions to members. Having your vendor in a 'mall' increases its exposure; it's very unlikely someone is going to visit your solo vendor out in the middle of nowhere unless you are willing to drop runes all over creation constantly.
I'd like to recommend you visit the
UO guide; it is a wiki-style database that can be quite handy for the returning player.
