These are potential deal-breakers as Obama and the Democratic-controlled Congress work to revamp the system to cover the nearly 50 million uninsured Americans and try to check rising medical costs.
"This is extremely complicated," says Senate Finance Committee Chairman Max Baucus, D-Mont.
He isn't kidding.
Even if lawmakers come back from their July Fourth recess charged up to tackle health care, these issues are going to keep simmering for months. A big blowup over any single one could threaten the entire legislation.
Here's a look at each issue, and how key players line up:
Covering nearly 50 million Americans won't come cheap. The government would have to subsidize premiums even for some middle-class families.
Baucus says he's pared down the cost of his bill to under $1 trillion over 10 years, but across the Capitol, House Democrats aren't yet revealing the price tag for their legislation. There's a reason. The more generous House version may cost a lot closer to $2 trillion.
Either way, that's a stunning amount of money. To put it in perspective, the United States will spend about $35 trillion on health care during the 10-year span of the legislation, so $1 trillion is about 3 percent of that.
Obama says the legislation will be fully paid for, and must not add to the deficit. But check the fine print: The cost estimates will only cover the first 10 years after the bill is signed. After that, the warranty expires.
Costs could explode in future years, particularly if the government is helping solid middle-class households pay for coverage, which already costs about $13,000 a year for a family plan.
The bigger the price tag, the more likely that trimming fat in the health care system won't cover costs and higher taxes will be needed sooner or later.
Republicans say the overhaul should be financed mainly with savings, even if it means delays in covering the uninsured, or helping fewer people.
Businesses now provide coverage to more than 160 million people, although no law says they must.
The health care legislation working its way through Congress is likely to include a requirement for individuals to get insurance.
Shouldn't it also spell out obligations for employers?
"It would seem to be unfair to exclude employers entirely and put the full force of responsibility on individuals," said former Senate Democratic leader Tom Daschle, who remains involved in the debate even though tax troubles forced him to withdraw as Obama's nominee for health secretary.
Both the House and Senate are considering new employer obligations. Businesses are strongly opposed to them.
Under the House Democrats' plan, employers would be required to provide coverage or pay a penalty.
The Senate Finance Committee is taking another approach. There wouldn't be any requirement that employers provide health insurance. But if a company's workers wind up getting taxpayer-subsidized insurance, the employer would have to pay part of the cost.
Obama supports a requirement, with exceptions for small businesses.
Republicans want to offer tax credits to help small companies buy coverage, and they oppose a requirement.
Employer opposition to health insurance requirements helped bring down President Bill Clinton's health plan in the 1990s, and business groups are already preparing for another fight.
It could get really ugly again.
Of all the divisive issues, Democrats' idea for a new government health plan to compete with private insurers has generated the most political passion.
It would mark the first time government gets into the business of providing medical insurance for middle-class workers and their families - a major expansion of its role.
The public plan would be available through a new kind of insurance purchasing pool called an exchange, which would also offer private plans. The purchasing pools would be open to individuals and small businesses.
Insurers, employers and congressional Republicans are adamantly opposed, saying the government would eventually drive out private coverage. Democrats are just as strongly in favor of the idea, saying the insurance industry needs competition. Attempts to find compromises, including setting up nonprofit co-ops, haven't defused the situation.
Obama offered a ringing defense of the public plan at his news conference last week. But would he refuse to sign a bill that doesn't have a government option?
"I'm not one to argue that if we don't get a public plan, we walk away," Daschle said. "I just can't imagine that not having a public plan would be sufficient reason to walk away from all the good we could do."
During last year's presidential campaign, Obama criticized Republican rival Sen. John McCain for proposing to tax workers who receive employer-provided health insurance to raise money for covering the uninsured.
Now the president may have to take back his words and break a campaign promise not to raise taxes on Americans making less than $250,000.
Although McCain's idea was far more sweeping, key senators are saying it won't be possible to pay for expanded coverage without taxing some health benefits.
The Senate Finance Committee is eyeing plans with a total premium cost above $17,000 for family coverage. The theory is that taxing such coverage - Obama calls it "Cadillac" - will encourage people to be thriftier consumers of medical services, and that can help bring down costs.
Labor unions are flabbergasted that Obama hasn't slammed the door on the idea.
McCain, who got a seat this year on the Senate Health, Education, Labor and Pensions Committee, will be watching closely.