I do not think that there is much I can add (that has not been said), but having organized 2 comps on my own, co-organized 1 and staffed almost every other comp I have attended, let me see if I can provide some tips.
1. In regards to organizing a comp by yourself, I would agree that it would really help you if you co-organized a competition with someone else first. There is quite a bit of work involved and if you have someone else you can divide that work load up, and see if that is something that you want to do on your own. I know of some people that have organized a comp before and after the comp they realized that organizing competitions is not for them and they preferred to instead help staff comps that they go to rather then organizing them. I personally enjoy hosting comps, and after doing it the first time makes the second time on easier, but if you have not staffed many comp (let alone organize one) then try to co-organize.
2. In regards to venue, look around for venues for a decent distance from where you live (or where you want to host a comp). How far to look is up to you, in how far you are willing to go, but I look for venues that were about 1 1/2 hours away from where I live, although I lucked out in finding a great venue only 30ish minutes away. Also, when looking for venues, look for places that you may not expect to works out. Some venues will be willing to help lower there rental fee, if you explain what you are trying to do, that you are on a somewhat tight budget etc. so ask around a see what you come across. Schools and churches tend to be good at that, but even science/learning related venues can be great with that as well. For instance, one venue I found (called something like "Discovery science center") was willing to allow me to use there venue for a huge discount since cubing (to some degree) is learning and using the brain in a different way (at least that is what the venue owner told me what he thought about cubing, haha).
3. For the cost related side of things, finding a venue that is cheap enough for a competition can be a bit more of a challenge, although even if you find a slightly higher rental fee for a venue, you can get that back in registration fees, and what ever you have left (after everything has been paid for) you can put aside and use that towards the next time you host a competition, or if you have a friend that wants to host a comp, you can help him/her out with the extra money that you have left from your comp.
And as it has already been said most delegates should/might be able to help cover the venue cost so that you can use the venue and then use some of the registration fees to help with that.
4. If you are really serious about hosting a comp (as I hope you are, since they are fun and it helps the cubing community out) then it will really help if you can plan ahead get a lot of the basic things done before/right after contacting the delegate, and that will (a) help the delegate out a bunch, and (b) show that you are serious and are really taking the time to organize a comp. Also, getting"the basic things done" are things like, creating a list of events, having a schedule, and having 2-3 dates in mind that will work for you and the venue (having a few dates tends to be much better, in case the delegate can not make one or two of them.
Hope some of this helps and please ask if you have any additional questions.