Navigating the submissions waters

I know the chances of getting published in print are very slim (I do have an e-book out there, though it's not exactly being grabbed by lots of people) but I would like to maximise my chances. I research what I can on the internet, but sometimes get confused. Could I ask you a few questions?

Firstly, simultaneous submissions. I understand why publishers wouldn't like them, but in my circumstances I feel almost impelled to have manuscripts at more than one publisher at the same time. Naturally I let them know this situation, and that I will inform them at once if anyone else accepts a piece of writing (unlikely, hence one of the reasons why I want to do it). Briefly, I am in my sixties, a recent survivor of cancer and healthy now, the sole income earner with lots of debt still and nearly 100 animals directly dependent on me to pay for their feed (this is no fault of my husband's); I drive four hours a day to and from work, have no real job security, work after hours as well, don't really have a life (including time to do any more writing). There are certainly people worse off than this, but I hope people would understand why I don't want to wait several months before trying the next publisher on the list. What is your view on this?

Secondly, I find a lot of publishers are demanding a detailed marketing plan. As someone who doesn't expect the plumber to fix my car too, I am a bit disheartened by this, especially as I live on a small farm, don't know anyone important and don't have time or money to get this sort of contact. I also have no experience of marketing whatsoever. Are they being reasonable? Do they really expect me to come up with a plan, and if so, how? (Sorry, this all sounds terribly negative!)

Lastly (and thanks for your patience), opinions seem to be many and varied as to whether one should have an agent. If you think it is generally a good idea, is it ethical or sensible to approach a would-be agent with samples from manuscripts already waiting at publishers, or should one choose a manuscript that is currently nowhere else?

First question: simultaneous submissions are completely acceptable, so long as you let publishers and agents know that that's what you're doing. If a publisher (or agent) doesn't want you to submit anywhere else at the same time, it's up to you whether you want to submit to them at all, but in my experience they all expect that authors send manuscripts to more than one publisher at the same time.

Second question: I can only presume you're talking about American publishers, as I don't know any Australian publishers who ask me for a detailed marketing plan, let alone an author. But I don't think American publishers expect marketing plans either. Without knowing more detail about who you're submitting to, I can only give a general response, which is that this requirement surprises me.

Third question: the previous two questions lead me to think that you DO need an agent, if only to navigate all these submissions and to give you advice about what you should or shouldn't be doing. As I've said in the past, not all authors need agents but it sounds like an agent could help manage things for you. When you're submitting to agents, you can submit manuscripts that are already at publishers but you need to disclose all information to the agent - i.e. say that it's on submission. The best manuscript to submit, though, is the one you're happiest with - and only submit one at a time. Most of us can only handle one at a time.