When a small job goes horribly wrong, calling in a professional immediately is a good idea. They may be able to salvage part of it, but their expertise could become an unexpected expense. Picking up the pieces when a family member has only done part of a job or done it wrong can be costly, so making sure the person doing the work really knows how to proceed can save time and money. It can also save hurt feelings by all parties involved.
Houses are not always built correctly, and modern codes are only applied when a new house is built or an existing one is upgraded. Opening up a wall to create a new window could show old and dangerous wiring, and calling the electrician is the only solution. A wise person should consider this possibility before starting, and they will then be prepared if a professional needs to be called.
Plumbing replacement is often a challenge, but it looks easy on a video. A large part of what plumbers do is ensure there are no leaks in the line, and it takes close attention for the amateur to follow their example. Everything might look perfect when the job is done, but turning on the water supply could show issues. Walking every part of the new plumbing line might be forgotten, and it could show up in water leaks days or weeks later when walls, ceilings, or floors are damaged.
Completing any work on the house can bring up side issues, so being prepared to call a local tradesman could be a good idea. If their help is unnecessary, a sigh of relief is just fine as the project is finished. Budgeting for their services might be a bit tight, but knowing a job has been completed correctly and safely could be the difference between happiness and a home disaster.