You asked

My wife wants another child but I'm not sure I'm ready. What should I do?

Concerns over time management are common amongst second-time parents. Examine your daily routine and figure out how you can make more time for yourselves. Consider preparing and freezing meals in advance; even 20 minutes saved per day can make a difference. If you can afford it, hire a domestic worker to do the washing and cleaning in your house.
Being financially secure is important. If you feel that you need more money to have another child, look for ways of increasing your earning; it may involve you or your wife working more hours. Consider the implications of working more and weigh up the time sacrifice. See if it is possible to cut back on household spending and if better financial management will make a difference.
If you are worried that you cannot give your second child the same love as you do the first, this should not be a concern. Even though it is a common concern among parents, the love you can feel for your children is boundless.
You may feel anxiety over possible difficulties your wife will go through during labour and pregnancy. Since your wife has to bear the risk and discomfort, talk to her about how she feels about another pregnancy. Make sure she is OK about the extra difficulty she has to go through while being a pregnant and already having a child.
If your first child has proven to be troublesome, remember that each child has a different temperament. Your second child will probably have a completely different temperament.
Spending time alone with your wife might already be problem. If you struggle to find time now, consider how little time you will have with a second child. Find ways that you can incorporate couple time in your schedule – even with a second child.
Examine your own childhood. Discuss your experiences with your wife; what it's like growing up as a single child or what effect a big age gap has on siblings. By engaging in a discussion with your wife over all these topics, you will probably find that you share the same feelings – although your wife will probably be more eager than you are, despite the obstacles.

More questions

Talking to an older child about a new baby is easier than explaining to a toddler or preschooler
How can you explain to a toddler that their is another baby on the way?
It is certainly possible to breastfeed while you are pregnant but you will need to get extra rest and nutrition. 
Getting older children to accept a new sibling can be a tricky proposition, but with time, patience and a bit of ingenuity, it is possible.
Whether or not having two or more children sharing a room will work for your family depends on a variety of factors.
The decision to have a second child is a difficult one to make. Openly sharing your concerns and discussing the implications with your wife is the best course of action.
While you may want your older children to be involved in caring for your new baby, it’s not always the best idea. There are other options however.
Signs that your toddler is progressing properly