暗网禁区

As you already found out, you can only register your address (and get a Meldebescheinigung) when you have a place to live in Germany. There is no way around that. So renting or buying one should be your first step.
If you cannot afford the deposit, you can possibly rent a temporary apartment or room in a hostel or similar (of course at much higher monthly costs).

The Meldebescheinigung is needed for your tax (Lohnsteuer) an social security (Sozialversicherung) numbers to be set up - which will happen automatically and takes a few weeks. You can also use it to open a bank account (at any bank of your liking - the differences are minor).

As far as I know, a student (immatriculated at a German university or institution) needs his own health insurance (at a subsidized rate of about 鈧�75/month) and cannot be covered by the spouse free of charge - but I may be wrong here. If you are not student by the above definition but have only minimal own income (鈧�450/month is already above the limit!) you can be covered in her insurance. If all this does not apply, you need your own insurance (at normal rates). Enquire about the options (and costs) at a public health insurer of your choice!

Note: All the above applies until the rules change in, as yet, unpredictable ways due to Brexit at the end of this year. In most likelyhood, you will then not have the EU citizen's right of free settlement any more and will need a family reunion visa - which requires a rental (or owned) flat for both of you together, German language at A1 or higher level and a secured source of your living expenses - approx. double of the 鈧�450/month, per person (this is also the minimum you need to survive at the poverty level).

Dear beppi,

I thank you very much for your response! Very helpful indeed.
It seems it all begins with obtaining my meldebesheinigung.
My in-laws have suggested that I can put down their address as my place of residence. Would this be an acceptable possibility? It would be only for a temporary basis, until I earn enough to pay my own deposit and rent out a place of my own.
My question regarding this is will they (my in-laws) be affected in anyway if I proceed with this method, such as additional taxes or possibly be required to be additional fees etc.
I thank you very much in advance for your responses

Kind regards

If your in-laws provide a room for you to live, they have to sign the required form 鈥淲ohnungsgeberbest脿tigung鈥� and you can of course register there.
Registering at an address you do not live at is illegal and can get you and the in-laws into great trouble (and a 鈧�50000 fine).
If they charge you a rent, they will be taxed on it. If not, you might under certain circumstances be taxed for the 鈥渕aterial benefits鈥� you receive as gift - but within the family the thresholds for this are so high that you will probably not eceed them.