Reading through S's post on Rule 58, I realized just a comment wasn't going to get it done for me! Must... post...
I don't like the "R" word at this point in general. Rules. So, I'll be going with the more semantically comfortable "guide line" term! The idea that it might not be a good idea to go into a relationship where there is a lack of parity in available relationship resources is something I've toyed with for quite a while. I've gone down that road a number of times, and more often than not, it doesn't go well. On the other hand, experience would lead me to believe that there are things that can be put into place up front to make this a more successful option!
#1- Be clear up front what it is you have to offer another partner in terms of emotional energy, time, and priority. Be clear with yourself first, and check in with your existing partners to do a veracity check on your grasp of the facts.
#2- Once you are reasonable sure you have a grip on that, share that information with your potential partner without sugar-coating it. This is one of those things where it is better to under-promise and over-deliver than the inverse. Don't say you have 3 nights a week free if you really can only put a bi-weekly commitment on the table consistently. Don't make out like you'll have daily phone calls if it's more likely to look like an email every few days.
#3- Talk about it. Bunches. Preferably before you get all sexified and emotionally vested. This whole top section applies to any relationship you are looking to expand into, not just ones with people who don't currently have a "primary".
This is a step that D and I spent a lot of time on before we began dating, and I think it was well worth the effort. He doesn't currently have another partner, and I was concerned, based on past experiences, that it would create an imbalance and pressure that would be uncomfortable for both of us. He spent the time to assess if what I had to offer would be comfortable and valuable to him, even though it wouldn't be able to meet some of his basic relationship needs and goals. Moreover, I asked him to think about if this would still be true when he does find a "primary", as being a "place holder relationship" wasn't something that I wanted for myself either.
#4- Know that things will change. Yep, best laid plans and all that jazz. The most well-considered strategy only lasts as long as things stay the same, and precisely how often does that happen? About half-past never, that's how often!
S and I started out being a primary/secondary dyad, where I was already in a primary relationship, but he wasn't, then I found that I had the capacity to have that level of emotional investment and practical responsibility to more than one person, and that relationship expanded out into a live in situation with kids and the whole nine. That wasn't the plan. That was about 10 years ahead of the plan. I'm glad I ditched the plan.
I've been with people who lost their main relationship or job during the course of our connection, and it threw the entire balance off. When someone you have a weekly date with suddenly has a ton of free time and energy on their hands, it can be really tempting for them to transfer that time and energy to another existing relationship, but that bandwidth may not be available. The constant feeling of not being able to perform up to a partner's standards or needs will erode things pretty quickly, in my experience.
#5- In the interests of dating people who are better equipped to answer #2 and 3, choose potential partners that have experience in considering the practical side of relationships on an emotional and logistical level.
Have they been a "secondary" partner before? Some people really like this zone of relationship, where there is emotional and physical intimacy, but less practical entanglement, intimacy with a lower demand level. Some people really dislike having a ceiling on how much time they may have available with someone, or how many overnights, or needing to consider other scheduled dates, work events etc. Dating someone who knows with some level of assurance that having this type of relationship will be comfortable and happy for them is a big plus!
For me, a significant consideration is parenting. If someone doesn't have/hasn't had kids, that takes a whole other level of examination. Will this person be supportive of the idea that I spend a couple nights a week helping my daughter at the rink? That my goal is to be available to help her with homework every day? That if something changes with my childcare arrangements, our "date" might look a lot more like snuggling on the couch with her between us entertained by a placid PG movie that neither of us might choose to ever watch, rather than a raucous evening out/in doing things that are decidedly more adult in nature?
If everyone involved has relationship or life experiences that they can translate into practical skills, it will put you far ahead of the game in determining if a potential relationship is going to be a positive experience for all concerned before you even begin.
What are some of the things that you consider before moving into "unbalanced" relationships, either as the partner with a high degree of relationship resources, or the one who is less resourced? What has led to an unfavorable relationship outcome for you? What are some strategies for success that you've found useful? Share your valuable experience with the rest of us!