Before buying Office or any software, you should do some research. First you should have a good knowledge of your business and any anticipated future business. You should be able to describe your business and business rules in plain English (no jargon). This description can start at extreme overview - the 30,000ft view - and then get progressively more detailed. The description should be clear and concise and recognizable and understandable by any and everyone in your business. That is it should be clear to all - not just an IT view or a Finance view.
From your business rules and description you should be able to build a data model of the "things" that are important to your business. Once you have the description and a data model, and solid list of your requirements, you can then compare "OTS" (off the shelf packages) and/or develop and build yourself or via contracted personnel. You do a cost/benefit analysis to some level to see what option(s) are most feasible/practical for your business. You look for database cost and maintenance, user interfaces, reporting, querying ... and be realistic in rating the various alternatives.
If you do decide, after analysis, to build your own system, you have to get training in database concepts, before any specific software (Access, MySql, SQL Server...).
Your questions are indicative of someone unsure of the steps involved in planning, designing, developing, testing and maintaining a database application. Beware of the marketers who want to sell you software --you need to make several decisions. Some of these decisions will be critical to your business, so don't approach this in a knee-jerk way and buy based on database software initial cost. You really have to do some research and most of it will be related to your business, its processes and business needs and priorities.
There are several inventory management, stock control are associated products on the market. There are lots of database management systems for sale. But you need to understand WHAT you need, then compare your needs with what is available. There are several posts in the forums; several videos(free) on youtube. You can also get trial versions of software...but you have to know what you need.
A friend of mine used to say--sure we can build anything it's just SMOP. Keep this in mind when you think of landing a person on the moon.(SMOP)
*SMOP -simple matter of programming.
Try searching google
https://www.google.com/search?q=inve...utf-8&oe=utf-8
this one for using Access for inventory management
https://www.google.com/search?q=inve...ement+msaccess
Here's a free generic data model for Customers and Inventory
http://databaseanswers.org/data_mode..._mgt/index.htm
There are several free videos re database concepts at the beginning of this link
https://www.accessforums.net/access/...tml#post221691
Getting started with database design - overview) available here
http://www.databaseanswers.org/approach2db_design.htm
Good luck. Let us know how you proceed.