Boston — A one-person household can seem, to the person in it at least, as much a three-ring circus as any growing family. If your life is a solo act, you know that nothing gets done around the house unless you do it yourself. There's no spouse to pick up the car from the shop, no kids to wheedle into biking to the store for the half-gallon of milk you forgot en route from the office.
And so some things just don't get done. Personal financial planning may be one of them. The relatively high discretionary income many singles have, plus a certain tendency to see singledom as a kind of halfway house preceding ''settling down,'' may also tend to work against setting up budgets and investment plans.
Moreover, the subtle social pressures that push married couples into thinking about insurance and wills and investments just aren't there for singles.
On the other hand, singles do have one big advantage over couples: when singles do buckle down to set financial goals, they find there's only one person to consult on what the priorities are, whether a vacation in the Caribbean or buying mutual funds.
Actually, financial planning is pretty much the same for singles and couples. The big difference is tax rates, says Claire Longden, first vice-president in charge of financial planning at the New York office of Butcher & Singer.
For 1983, the 50 percent tax bracket will begin at $109,000 of taxable income for those filing a joint return - and only $55,000 for those filing single returns. These high rates mean it's harder for singles to get the cash together to ''redeploy the assets,'' Ms. Longden says.
One quick suggestion she has for singles is to park one's IRA funds in zero-coupon bonds, maturing in the year 2000. If $1,700 is put into such bonds now, it will become $10,000 by maturity. As corporate bonds, these are taxable on an amortized basis year by year - but not if they are in an IRA.
''Inflation's going to take its toll, but you're not prone to the same vagaries as putting it into stocks and hoping,'' Ms. Longden says.
She also urges singles, in particular, to be sure they are well protected against disability.
In theory at least, financial planning should be basically the same for men and women, she says.
But the word from the front is that, despite some years of feminist consciousness raising, there are still lots of women out there with little idea of how to set their own financial goals - or even balance a checkbook. Getting into law school can seem easier than setting up a budget.
Ms. Longden tells of a young woman who knew she had trust payments coming in every month, but that was about all she knew about her finances. ''We started working with her and found out she was worth some $2 million to $3 million.
''Her brother was in the same position - but he had been taught about it.''
Butcher & Singer has been working with the woman for about a year and now she's doing fine.
Not everyone has quite the same problems as Ms. Longden's unwitting millionairess.
''Women, once they get into (financial planning) are super, super bright, but some of them still feel there's a certain mystique to it all, that it's still super-complicated.''
She laments what she sees as a male tendency to use buzzwords instead of plain English. Perhaps not coincidentally, two of the books she recommends as ''homework'' for those making their first venture into serious financial planning are written by women: ''The Power of Money Dynamics,'' by Venita VanCaspel and Adriane G. Berg's ''Moneythink.''
Many women still find that male financial advisers treat them in patronizing fashion.
''A woman came in to me the other day,'' Ms. Longden recouts, ''saying, 'Claire, can you please handle my portfolio?' She'd gone to see the trust adviser at some company, and she said, 'He sat there and blew cigar smoke in my face and said, ''What can I do for you, honey?'' ' ''
Ms. Longden says, ''I think men don't realize they do that, but women just aren't going to stand for it.''
The best way around this? She says it sounds self-serving, but she suggests women go to a female financial planner. She speaks of a new ''network'' that is developing in which one professional woman suggests her broker to another. A woman often simply feels greater rapport with another woman when it comes to planning.
One group that is likely to need special attention is older women who have left financial matters completely to their husbands, whose estates they may suddenly inherit. ''It may be difficult, but these women should go, with their husbands, to a financial planner to find out what it's all about.''
She finds it hard to be dogmatic about the income level at which one should seek professional help in financial planning, but suggests a pre-tax income of $ 75,000 annually as the line.
Below that, people should be reading, gathering ideas, familiarizing themselves with the financial marketplace, and getting some sense of where they expect their earning power to go. She particularly recommends the VanCaspel book for its lucid descriptions of the kinds of financial products that are available.
Singles in their 20s and 30s and earning some $20,000 to $40,000 annually are at the ''homework'' stage.
Ms. Longden advises women needing to branch out into more dynamic investments to let their ''risk level'' develop slowly. If they ''waste'' a year getting used to higher risks, so be it, she says.
Deciding what one's risk level should be is key to sound planning for men and women.
''A young professional woman with her own business, earning well, may decide she's got 10 good earning years ahead of her before she marries and has children ,'' Ms. Longden says, ''and so she can afford to take lots of risk.''
Women have to be philosophical - if they're going to have children, It's likely to be before they're 40, she notes.
''At the other extreme'' - and here Ms. Longden emphasizes that she doesn't like to pigeonhole people - ''is the young man planning to marry soon, potentially a nonearner,'' or a woman who earns significantly less than he.
Especially is such a couple want to have children soon, the groom-to-be should be conservative in his investments.
But flexibility is essential to sound planning. Three years is about as far into the future as plans can be made, Ms. Longden says: ''Think back three years - what do we know now that we didn't know then? Just look at prime rate over this time. We've seen it a 8 percent, and then it went up to 20 percent, and now it's down again. You can't plan for 20 years.''
Real estate, she suggests, is still a good first investment: ''Rent money is wasted money; buying your own apartment makes sense. It's a roof over your head, it's a tax break, and it's an investment.''
The mortgage rates of recent years have been obstacle to this big investment, but not an insurmountable one. Over the past couple of years Ms. Longden has advised clients contemplating mortgages at 16, 17, or 18 percent to be sure they have some sort of out, such as possible renegotiation.