It depends on (1) where you live and (2) whether you use an agency. In the SF Bay Area it is expensive. Agency nurses cost $60/hr or more. But if you post a want-ad on indeed.com, you can easily find licensed vocational nurses (LVNs) for under $20/hr, based on experience. This is because the local nursing homes pay them $19/hr, and many would rather work for you than work in a nursing home. If you live in a rural area, it will cost less.
If you only need help with activities of daily living (transferring, eating, toileting, etc.), you can easily find certified nursing assistants (CNAs) on indeed.com for $12-14/hr. Again, this is how much the area facilities are currently paying them.
When your need for skilled nursing services such as tracheal suctioning or G-tube feeding becomes a big part of the job, you may find it hard to find CNAs who will stick with you, as most of them are looking for easier gigs. Also, unlike nurses, CNAs who want to quit have no legal obligation to stick with you until a replacement is available. So you are smart to plan for eventual nursing care.
Also, if you have a good health policy, your insurance may cover a lot of your care. In California, Kaiser commercial policies allow you to trigger hospice benefits as soon as any doctor gives you a life expectancy of one year or less (that's right--one year--not 6 months). Kaiser's hospice coverage includes 24-hour skilled nursing and home health aide care. Kaiser bean counters will fight to deny this coverage on the basis that you do not need nursing care, but California law requires a nursing license for tracheal suctioning and G-tube feeding, so you can expect to win that fight, as we did. So take a good look at your health policy and see what it provides.
--Dave